I have this function a student represented by id going to add a course in a specific semester. this code is correct but i don't understand the section when he did
for (size_t i = 0; i < (*iteratorVectorP).size(); i++) ...
void add_course(map<int, map<int, vector<course *> * > > &DB, int
semester, int id, course c)
{
auto iterator = DB.find(id); //find id as key, set map to value
vector<course*> *pointer = new vector<course*>;
if (iterator != DB.end())
{
auto iterator1 = ((*iterator).second).find(semester); //find
semester as key, set vector to value
if (iterator1 == (*iterator).second.end()) //if semester does not exist
{
pointer->push_back(new course(c));
(iterator->second)[semester] = pointer;
}
else //if semester exist
{
auto iteratorVectorP = (iterator->second)[semester];
// i do not understand what his doing here
for (size_t i = 0; i < (*iteratorVectorP).size(); i++)
{
if (c == *(*iteratorVectorP)[i])
{
return; //exit when class exist
}
else
{
(*iteratorVectorP).push_back(new course(c));
return;
}
}
}
}
}
the defination of iteratorVectorP is vector, so the for loop is iterating the course and try to add it in the vector if non-existed.
It looks like iteratorVectorP is a pointer, so calling (*iteratorVectorP).size() will get the value it is pointing to.
Related
I have no idea where the segmentation error is coming from ... Any ideas?
I am working with structures for an assignment
TestResult testResultFactory(std::string name, double mark)
{
//creating an object of TestResult
TestResult car;
car.name = name;
car.mark = mark;
return car;
}
Student studentFactrory(std::string name)
{
//Creating an object of student
Student house;
house.name = name;
house.testResults = 0;
house.numTestResults = 0;
return house;
}
void addTestResult(Student * student, std::string testName, double testMark)
{
//First we need to create a new array
(student->numTestResults)+=1;
TestResult *newTestArray = new TestResult[(student->numTestResults)];
//Now we loop through the old array and add it to the new one
int index = (student->numTestResults);
for (size_t i = 0; i < (index-1); i++)
{
newTestArray[i] = testResultFactory((student->testResults[i].name),(student->testResults[i].mark));
}
//Now we need to add the new student to the end of the array
newTestArray[index] = testResultFactory(testName, testMark);
(student->testResults) = newTestArray;
}
string studentBest(Student const * student)
{
//create variables as temps
string highestName;
double highestMark;
int index = (student->numTestResults);
//Setting the two variables to the first value
highestName = (student->testResults[0].name);
highestMark = (student->testResults[0].mark);
//Using a while loop to compare and get the best
for (size_t i = 0; i < index; i++)
{
if((student->testResults[i].mark)> highestMark)
{
highestMark = (student->testResults[i].mark);
highestName = (student->testResults[i].name);
}
}
//returning the string they want
string send = (highestName)+ " "+ doubleToString(highestMark)+ "%";
return send;
}
double studentAverage(Student const * student)
{
//Variables used as temps
double average = 0;
double counter = 0.0;
double running = 0;
int index = (student->numTestResults);
//Now we need to loop through each one and add to running and counter
for (size_t i = 0; i < index; i++)
{
counter++;
running += (student->testResults[i].mark);
}
//calculating the average;
average = (running)/counter;
return average;
}
void destroyStudent(Student * student)
{
delete [] (student->testResults);
(student->testResults)=0;
}
Subject subjectFactory(std::string name)
{
//Creating an object to use in subject factory
Subject lamp;
lamp.name = name;
lamp.numStudents = 0;
lamp.studentsAllocated = 0;
lamp.students = 0;
return lamp;
}
MY guess is that the error occurs because of an out of bounds array or an pointer not worked with correctly .
int getStudentIndex(Subject const * subject, std::string studentName)
{
int index;
int count = (subject->numStudents);
//loop to find the names and set index
for (size_t i = 0; i < count; i++)
{
if(studentName == ((subject->students[i].name)))
{
index = i;
}
else index = -1;
}
return index;
}
void addStudent(Subject * subject, std::string studentName)
{
//Variables as temps
Student *pointer =0;
int index = getStudentIndex(subject,studentName);
if(index != -1)
{
//Now we need to see if they are large enough
if((subject->studentsAllocated)==0)
{
//Set the allocated to 2
(subject->studentsAllocated) = 2;
pointer = new Student[2];
//Figure this out later
pointer[1] = studentFactrory(studentName);
(subject->students) = pointer;
}
else
{
//increase SA with 1.5
(subject->studentsAllocated) = (subject->studentsAllocated) * 1.5;
pointer = new Student[(subject->studentsAllocated)+1];
int count = (subject->studentsAllocated);
//Now we need to put all the other students in
for (size_t i = 0; i < count-1; i++)
{
pointer[i] = (subject->students[i]);
}
pointer[(subject->studentsAllocated)+1] = studentFactrory(studentName);
(subject->studentsAllocated) += 1 ;
}
//Once done just seet one equal to
(subject->students) = pointer;
}
else return;
}
void removeStudent(Subject * subject, std::string studentName)
{
//First get temps
int index = getStudentIndex(subject ,studentName);
int number = (subject->studentsAllocated);
int i = index;
//delete student
if(index == -1) return;
destroyStudent(&(subject->students)[index]);
//loop to shift the things
while (i<(number -1))
{
(subject->students)[i] = (subject-> students[i+1]);
}
//Removing the last one
(subject->numStudents) -= 1;
}
bool addTestResult(Subject * subject, std::string studentName, std::string testName, double testMark)
{
int index = getStudentIndex(subject ,studentName);
if(index != -1)
{
addTestResult(&(subject->students [index]),testName,testMark);
return true;
}
else
return false;
}
void printSubjectSummary(Subject const * subject)
{
cout<<(subject->name)<< ": with "<<(subject->numStudents)<<" students"<<endl;
//Variables to use in the loop
size_t indexLoop = subject->numStudents;
int i=0;
while (i< indexLoop)
{
cout<<(subject->students[i].name)<<" Average: "<<studentAverage(&(subject->students[i]))<<", Best: "<<studentBest(&(subject->students[i]))<<endl;
}
}
void destroySubject(Subject * subject)
{
//Variables
size_t indexLoop = subject->numStudents;
for (size_t i = 0; i < indexLoop; i++)
{
destroyStudent(&(subject->students[i]));
}
delete [] subject->students;
subject->students =0;
}
I can not seem to find where the segmentation error is coming from. Even restarted the whole assignment from scratch and still seem to get errors.
Can someone please help or indicate where the fault could be coming from.
Over here we have the structs.h file that is included in my code above
#ifndef STRUCTS_H
#define STRUCTS_H
struct TestResult{
double mark;//the test mark as a percentage
std::string name;//the test name
};
struct Student{
std::string name;
TestResult * testResults;//an arry of TestResults
size_t numTestResults;//the number of results for this student (also the size of the array)
};
struct Subject{
std::string name;
Student * students;//an array of Students
size_t numStudents;//the number of students added to the subject
size_t studentsAllocated;//the size of the Student arry(must never be smaller that numStudents)
};
#endif
There are so many logical errors in there that the root cause (or causes; there are quite a few candidates) could be pretty much anywhere.
getStudentIndex returns -1 unless the student is the last one in the array, and an indeterminate value for the first one you add, so adding the first student to a subject is undefined.
addStudent only adds a student if they're already taking the subject.
It also (for some inexplicable reason) allocates an array of two Students, leaving the first element uninitialised.
Using this first element is, of course, undefined.
In the other branch, it first claims that the number of allocated students is * 1.5, but then only allocates + 1.
This will undoubtedly lead to problems.
There is a recursion in addTestResult that will never terminate.
There are most likely other problems as well – this was just a quick glance.
Start with fixing these.
And do learn about constructors and destructors so you can get rid of those "factory" and "destroy" functions.
I'm having a problem with the code attached below. Essentially it generates a huge memory leak but I can't see where it happens.
What the code does is receiving an array of strings, called prints, containing numbers (nodes) separated by ',' (ordered by desc number of nodes), finding other compatible prints (compatible means that the other string has no overlapping nodes 0 excluded because every print contains it) and when all nodes are covered it calculates a risk function on the basis of a weighted graph. In the end it retains the solution having the lowest risk.
The problem is that leak you see in the picture. I really can't get where it comes from.
Here's the code:
#include "Analyzer.h"
#define INFINITY 999999999
// functions prototypes
bool areFullyCompatible(int *, int, string);
bool contains(int *, int, int);
bool selectionComplete(int , int);
void extractNodes(string , int *, int &, int);
void addNodes(int *, int &, string);
Analyzer::Analyzer(Graph *graph, string *prints, int printsLen) {
this->graph = graph;
this->prints = prints;
this->printsLen = printsLen;
this->actualResult = new string[graph->nodesNum];
this->bestResult = new string[graph->nodesNum];
this->bestReSize = INFINITY;
this->bestRisk = INFINITY;
this-> actualSize = -1;
}
void Analyzer::getBestResult(int &size) {
for (int i = 0; i < bestReSize; i++)
cout << bestResult[i] << endl;
}
void Analyzer::analyze() {
// the number of selected paths is at most equal to the number of nodes
int maxSize = this->graph->nodesNum;
float totRisk;
int *actualNodes = new int[maxSize];
int nodesNum;
bool newCycle = true;
for (int i = 0; i < printsLen - 1; i++) {
for (int j = i + 1; j < printsLen; j++) {
// initializing the current selection
if (newCycle) {
newCycle = false;
nodesNum = 0;
extractNodes(prints[i], actualNodes, nodesNum, maxSize);
this->actualResult[0] = prints[i];
this->actualSize = 1;
}
// adding just fully compatible prints
if (areFullyCompatible(actualNodes, nodesNum, prints[j])) {
this->actualResult[actualSize] = prints[j];
actualSize++;
addNodes(actualNodes, nodesNum, prints[j]);
}
if (selectionComplete(nodesNum, maxSize)) {
// it means it's no more a possible best solution with the minimum number of paths
if (actualSize > bestReSize) {
break;
}
// calculating the risk associated to the current selection of prints
totRisk = calculateRisk();
// saving the best result
if (actualSize <= bestReSize && totRisk < bestRisk) {
bestReSize = actualSize;
bestRisk = totRisk;
for(int k=0;k<actualSize; k++)
bestResult[k] = actualResult[k];
}
}
}
newCycle = true;
}
}
float Analyzer::calculateRisk() {
float totRisk = 0;
int maxSize = graph->nodesNum;
int *nodes = new int[maxSize];
int nodesNum = 0;
for (int i = 0; i < actualSize; i++) {
extractNodes(this->actualResult[i], nodes, nodesNum, maxSize);
// now nodes containt all the nodes from the print but 0, so I add it (it's already counted but misses)
nodes[nodesNum-1] = 0;
// at this point I use the graph to calculate the risk
for (int i = 0; i < nodesNum - 1; i++) {
float add = this->graph->nodes[nodes[i]].edges[nodes[i+1]]->risk;
totRisk += this->graph->nodes[nodes[i]].edges[nodes[i+1]]->risk;
//cout << "connecting " << nodes[i] << " to " << nodes[i + 1] << " with risk " << add << endl;
}
}
delete nodes;
return totRisk;
}
// -------------- HELP FUNCTIONS--------------
bool areFullyCompatible(int *nodes, int nodesNum, string print) {
char *node;
char *dup;
int tmp;
bool flag = false;
dup = strdup(print.c_str());
node = strtok(dup, ",");
while (node != NULL && !flag)
{
tmp = atoi(node);
if (contains(nodes, nodesNum, tmp))
flag = true;
node = strtok(NULL, ",");
}
// flag signals whether an element in the print is already contained. If it is, there's no full compatibility
if (flag)
return false;
delete dup;
delete node;
return true;
}
// adds the new nodes to the list
void addNodes(int *nodes, int &nodesNum, string print) {
char *node;
char *dup;
int tmp;
// in this case I must add the new nodes to the list
dup = strdup(print.c_str());
node = strtok(dup, ",");
while (node != NULL)
{
tmp = atoi(node);
if (tmp != 0) {
nodes[nodesNum] = tmp;
nodesNum++;
}
node = strtok(NULL, ",");
}
delete dup;
delete node;
}
// verifies whether a node is already contained in the nodes list
bool contains(int *nodes, int nodesNum, int node) {
for (int i = 0; i < nodesNum; i++)
if (nodes[i] == node)
return true;
return false;
}
// verifies if there are no more nodes to be added to the list (0 excluded)
bool selectionComplete(int nodesNum, int maxSize) {
return nodesNum == (maxSize-1);
}
// extracts nodes from a print add adds them to the nodes list
void extractNodes(string print, int *nodes, int &nodesNum, int maxSize) {
char *node;
char *dup;
int idx = 0;
int tmp;
dup = strdup(print.c_str());
node = strtok(dup, ",");
while (node != NULL)
{
tmp = atoi(node);
// not adding 0 because every prints contains it
if (tmp != 0) {
nodes[idx] = tmp;
idx++;
}
node = strtok(NULL, ",");
}
delete dup;
delete node;
nodesNum = idx;
}
You have forgotten to delete several things and used the wrong form of delete for arrays where you have remembered, e.g.
float Analyzer::calculateRisk() {
float totRisk = 0;
int maxSize = graph->nodesNum;
int *nodes = new int[maxSize];
//...
delete [] nodes; //<------- DO THIS not delete nodes
The simplest solution is to avoid using raw pointers and use smart ones instead. Or a std::vector if you just want to store stuff somewhere to index into.
You have new without corresponding delete
this->actualResult = new string[graph->nodesNum];
this->bestResult = new string[graph->nodesNum];
These should be deleted somewhere using delete [] ...
You allocate actualNodes in analyze() but you don't release the memory anywhere:
int *actualNodes = new int[maxSize];
In Addition, Analyzer::bestResult and Analyzer::actualResult are allocated in the constructor of Analyzer but not deallocated anywhere.
this->actualResult = new string[graph->nodesNum];
this->bestResult = new string[graph->nodesNum];
If you must use pointers, I really suggest to use smart pointers, e.g. std::unique_ptr and/or std::shared_ptr when using C++11 or later, or a Boost equivalent when using C++03 or earlier. Otherwise, using containers, e.g. std::vector is preferred.
PS: You're code also has a lot of mismatches in terms of allocation and deallocation. If memory is allocated using alloc/calloc/strdup... it must be freed using free. If memory is allocated using operator new it must be allocated with operator delete. If memory is allocated using operator new[] it must be allocated with operator delete[]. And I guess you certainly should not delete the return value of strtok.
So I thought I understood how to implement an array of pointers but my compiler says otherwise =(. Any help would be appreciated, I feel like I'm close but am missing something crucial.
1.) I have a struct called node declared:.
struct node {
int num;
node *next;
}
2.) I've declared a pointer to an array of pointers like so:
node **arrayOfPointers;
3.) I've then dynamically created the array of pointers by doing this:
arrayOfPointers = new node*[arraySize];
My understanding is at this point, arrayOfPointers is now pointing to an array of x node type, with x being = to arraySize.
4.) But when I want to access the fifth element in arrayOfPointers to check if its next pointer is null, I'm getting a segmentation fault error. Using this:
if (arrayOfPointers[5]->next == NULL)
{
cout << "I'm null" << endl;
}
Does anyone know why this is happening? I was able to assign a value to num by doing: arrayOfPointers[5]->num = 77;
But I'm confused as to why checking the pointer in the struct is causing an error. Also, while we're at it, what would be the proper protoype for passing in arrayOfPointers into a function? Is it still (node **arrayOfPointers) or is it some other thing like (node * &arrayOfPointers)?
Thanks in advance for any tips or pointers (haha) you may have!
Full code (Updated):
/*
* Functions related to separate chain hashing
*/
struct chainNode
{
int value;
chainNode *next;
};
chainNode* CreateNewChainNode (int keyValue)
{
chainNode *newNode;
newNode = new (nothrow) chainNode;
newNode->value = keyValue;
newNode->next = NULL;
return newNode;
}
void InitDynamicArrayList (int tableSize, chainNode **chainListArray)
{
// create dynamic array of pointers
chainListArray = new (nothrow) chainNode*[tableSize];
// allocate each pointer in array
for (int i=0; i < tableSize; i++)
{
chainListArray[i]= CreateNewChainNode(0);
}
return;
}
bool SeparateChainInsert (int keyValue, int hashAddress, chainNode **chainListArray)
{
bool isInserted = false;
chainNode *newNode;
newNode = CreateNewChainNode(keyValue); // create new node
// if memory allocation did not fail, insert new node into hash table
if (newNode != NULL)
{
//if array cell at hash address is empty
if (chainListArray[hashAddress]->next == NULL)
{
// insert new node to front of list, keeping next pointer still set to NULL
chainListArray[hashAddress]->next = newNode;
}
else //else cell is pointing to a list of nodes already
{
// new node's next pointer will point to former front of linked list
newNode->next = chainListArray[hashAddress]->next;
// insert new node to front of list
chainListArray[hashAddress]->next = newNode;
}
isInserted = true;
cout << keyValue << " inserted into chainListArray at index " << hashAddress << endl;
}
return isInserted;
}
/*
* Functions to fill array with random numbers for hashing
*/
void FillNumArray (int randomArray[])
{
int i = 0; // counter for for loop
int randomNum = 0; // randomly generated number
for (i = 0; i < ARRAY_SIZE; i++) // do this for entire array
{
randomNum = GenerateRandomNum(); // get a random number
while(!IsUniqueNum(randomNum, randomArray)) // loops until random number is unique
{
randomNum = GenerateRandomNum();
}
randomArray[i] = randomNum; // insert random number into array
}
return;
}
int GenerateRandomNum ()
{
int num = 0; // randomly generated number
// generate random number between start and end ranges
num = (rand() % END_RANGE) + START_RANGE;
return num;
}
bool IsUniqueNum (int num, int randomArray[])
{
bool isUnique = true; // indicates if number is unique and NOT in array
int index = 0; // array index
//loop until end of array or a zero is found
//(since array elements were initialized to zero)
while ((index < ARRAY_SIZE) && (!randomArray[index] == 0))
{
// if a value in the array matches the num passed in, num is not unique
if (randomArray[index] == num)
{
isUnique = false;
}
index++; // increment index counter
} // end while
return isUnique;
}
/*
*main
*/
int main (int argc, char* argv[])
{
int randomNums[ARRAY_SIZE] = {0}; // initialize array elements to 0
int hashTableSize = 0; // size of hash table to use
chainNode **chainListArray;
bool chainEntry = true; //testing chain hashing
//initialize random seed
srand((unsigned)time(NULL));
FillNumArray(randomNums); // fill randomNums array with random numbers
//test print array
for(int i = 0; i < ARRAY_SIZE; i++)
{
cout << randomNums[i] << endl;
}
//test chain hashing insert
hashTableSize = 19;
int hashAddress = 0;
InitDynamicArrayList(hashTableSize, chainListArray);
//try to hash into hash table
for (int i = 0; i < ARRAY_SIZE; i++)
{
hashAddress = randomNums[i] % hashTableSize;
chainEntry = SeparateChainInsert(randomNums[i], hashAddress, chainListArray);
}
system("pause");
return 0;
}
arrayOfPointers = new node*[arraySize];
That returns a bunch of unallocated pointers. Your top level array is fine, but its elements are still uninitialized pointers, so when you do this:
->next
You invoke undefined behavior. You're dereferencing an uninitialized pointer.
You allocated the array properly, now you need to allocate each pointer, i.e.,
for(int i = 0; i < arraySize; ++i) {
arrayOfPointers[i] = new node;
}
As an aside, I realize that you're learning, but you should realize that you're essentially writing C here. In C++ you have a myriad of wonderful data structures that will handle memory allocation (and, more importantly, deallocation) for you.
Your code is good, but it's about how you declared your InitDynamicArrayList. One way is to use ***chainListArray, or the more C++-like syntax to use references like this:
void InitDynamicArrayList (int tableSize, chainNode **&chainListArray)
I'am facing a problem which should be solved using Aho-Corasick automaton. I'am given a set of words (composed with '0' or '1') - patterns and I must decide if it is possible to create infinite text, which wouldn't contain any of given patterns. I think, the solution is to create Aho-Corasick automaton and search for a cycle without matching states, but I'm not able to propose a good way to do that. I thought of searching the states graph using DFS, but I'm not sure if it will work and I have an implementation problem - let's assume, that we are in a state, which has an '1' edge - but state pointed by that edge is marked as matching - so we cannot use that edge, we can try fail link (current state doesn't have '0' edge) - but we must also remember, that we could not go with '1' edge from state pointed by fail link of the current one.
Could anyone correct me and show me how to do that? I've written Aho-Corasick in C++ and I'am sure it works - I also understand the entire algorithm.
Here is the base code:
class AhoCorasick
{
static const int ALPHABET_SIZE = 2;
struct State
{
State* edge[ALPHABET_SIZE];
State* fail;
State* longestMatchingSuffix;
//Vector used to remember which pattern matches in this state.
vector< int > matching;
short color;
State()
{
for(int i = 0; i < ALPHABET_SIZE; ++i)
edge[i] = 0;
color = 0;
}
~State()
{
for(int i = 0; i < ALPHABET_SIZE; ++i)
{
delete edge[i];
}
}
};
private:
State root;
vector< int > lenOfPattern;
bool isFailComputed;
//Helper function used to traverse state graph.
State* move(State* curr, char letter)
{
while(curr != &root && curr->edge[letter] == 0)
{
curr = curr->fail;
}
if(curr->edge[letter] != 0)
curr = curr->edge[letter];
return curr;
}
//Function which computes fail links and longestMatchingSuffix.
void computeFailLink()
{
queue< State* > Q;
root.fail = root.longestMatchingSuffix = 0;
for(int i = 0; i < ALPHABET_SIZE; ++i)
{
if(root.edge[i] != 0)
{
Q.push(root.edge[i]);
root.edge[i]->fail = &root;
}
}
while(!Q.empty())
{
State* curr = Q.front();
Q.pop();
if(!curr->fail->matching.empty())
{
curr->longestMatchingSuffix = curr->fail;
}
else
{
curr->longestMatchingSuffix = curr->fail->longestMatchingSuffix;
}
for(int i = 0; i < ALPHABET_SIZE; ++i)
{
if(curr->edge[i] != 0)
{
Q.push(curr->edge[i]);
State* state = curr->fail;
state = move(state, i);
curr->edge[i]->fail = state;
}
}
}
isFailComputed = true;
}
public:
AhoCorasick()
{
isFailComputed = false;
}
//Add pattern to automaton.
//pattern - pointer to pattern, which will be added
//fun - function which will be used to transform character to 0-based index.
void addPattern(const char* const pattern, int (*fun) (const char *))
{
isFailComputed = false;
int len = strlen(pattern);
State* curr = &root;
const char* pat = pattern;
for(; *pat; ++pat)
{
char tmpPat = fun(pat);
if(curr->edge[tmpPat] == 0)
{
curr = curr->edge[tmpPat] = new State;
}
else
{
curr = curr->edge[tmpPat];
}
}
lenOfPattern.push_back(len);
curr->matching.push_back(lenOfPattern.size() - 1);
}
};
int alphabet01(const char * c)
{
return *c - '0';
}
I didn't look through your code, but I know very simple and efficient implementation.
First of all, lets add Dictionary Suffix Links to the tree (their description you can find in Wikipedia). Then you have to look through all your tree and somehow mark matching nodes and nodes that have Dict Suffix Links as bad nodes. The explanation of these actions is obvious: you don't need all the matching nodes, or nodes that have a matching suffix in them.
Now you have an Aho-Corasick tree without any matching nodes. If you just run DFS algo on the resulting tree, you will get what you want.
I am trying to sort an array of int and chars (from a class) by descending order. These are student names and grades.
The class is defined as:
class Student {
public:
char name[20];
int grades;
};
numCount is the incremental value of number of records.
void bubble_sort(Student theResults[], int numCount)
{
bool swapped = true;
while(swapped)
{
swapped = false;
for(int i=1;i<numCount;i++)
{
if(theResults[i-1].grades < theResults[i].grades)
{
int tempHold = theResults[i-1].grades;
theResults[i-1].grades = theResults[i].grades;
theResults[i].grades = tempHold;
swapped = true;
}
}
}
The issue I am having is that the int values (grades) are sorted correctly after the loop but having difficulty getting the names to be correctly allocated to match with the grades.
I have used the following code but it doesn't work as it displays the incorrect grades for the students.
char* title_temp = theResults[i-1].name;
theResults[i-1].name[20] = theResults[i].name[20];
theResults[i].name[20] = title_temp[20];
I think your problem is here:
if(theResults[i-1].grades < theResults[i].grades)
{
int tempHold = theResults[i-1].grades;
theResults[i-1].grades = theResults[i].grades;
theResults[i].grades = tempHold;
swapped = true;
}
What you really want to do is
if(theResults[i-1].grades < theResults[i].grades)
{
Student tempHold = theResults[i-1];
theResults[i-1] = theResults[i];
theResults[i] = tempHold;
swapped = true;
}
Before all you were changing was the grade value and not the names, this will switch the entire Student object and should produce the output you are looking for
You'd have to copy the entire char block, each element at a time using a loop, or you could use memcpy.
You could also use a shallow copy of your class
void bubble_sort(Student theResults[], int numCount)
{
bool swapped = true;
while(swapped)
{
swapped = false;
for(int i=1;i<numCount;i++)
{
if(theResults[i-1].grades < theResults[i].grades)
{
Student tempHold = theResults[i-1];
theResults[i-1]= theResults[i];
theResults[i] = tempHold;
swapped = true;
}
}
}
}
The problem is that you need to swap the objects, the grades only have to act as a key to guide the sort, try this :
void bubble_sort(Student theResults[], int numCount)
{
Student tempHold;
bool swapped = true;
while(swapped)
{
swapped = false;
for(int i=1;i<numCount;i++)
{
if(theResults[i-1].grades < theResults[i].grades)
{
tempHold = theResults[i-1]; //swap the objects, not just the grades.
theResults[i-1]= theResults[i];
theResults[i] = tempHold;
swapped = true;
}
}
}}
However, if you must copy members, then in addition to swapping grades :
char temp[20];
strcpy(temp ,theResults[i-1].name);
strcpy(theResults[i-1].name,theResults[i].name);
strcpy(theResults[i].name,temp);
Instead of using
char* title_temp = theResults[i-1].name; // <-wrong
theResults[i-1].name[20] = theResults[i].name[20];//20 is invalid index
theResults[i].name[20] = title_temp[20]; //this is just 1 element out of the whole array
which is wrong due to many reasons.