My code is behaving really weird. It works sometimes and it crashes at other times.
When it crashes it says:
a problem caused the program to stop working correctly
My main:
int main() {
start();
Read();
cout << "Enter the code of the course: ";
cin >> coursecode;
cout << "\n1111111\n";
searchCourse(coursecode);
cout << "\n222222\n";
return 0;
}
I wrote two couts above and below my searchCourse function to see if the program compiles all the lines. It really does compile everything, and at the end it prints 222222 before crashing.
The start method just creates an array of BinaryTree objects then store the
student data (they are read from text file) according to their courses.
start():
BinaryTree *a[10];
void start()
{
for(int g=1;g<=10;g++)
{
a[g] = new BinaryTree(g);
}
}
searchCourse():
void searchCourse(string code)
{
for(int j=1;j<=count;j++)
{
if(a[j]->checkit(code)!=0)
{
a[j]->display();
break;
}
}
}
Checkit() in BinaryTree.h:
bool checkit(string m)
{
if (root==NULL)
return false;
else
if(root->data.getCourse()==m)
return true;
else
return false;
}
BinaryTree *a[10];
for(int g=1;g<=10;g++)
{
a[g] = new BinaryTree(g);
}
Would have a memory exception. You have an array of 10, and you are trying to access the 11th element (since you go until g<=10, and a[10] is the eleventh element). Use:
for(int g=0;g<10;g++)
instead. You may have to also do new BinaryTree(g+1); if Binary Tree starts at 1.
This is an error that is in other places in your code as well, like for(int j=1;j<=count;j++) (for(int j=0;j<count;j++) is probably what you want).
Arrays start at 0. Why does the indexing start with zero in 'C'?
Related
this simple loop method is unable to run and an error arises "app crashed". when i checked this in an online compiler it gave 'segmentation fault(core dumped)'-
string studies(setMatter ch) {
string a = "LISTEN CAREFULLY!\n";
int i = 0;
while (i <= ch.a.quantity()) {
a += ch.a.getAns(i);
i++;
}
return a;
}
also see for reference of methods in the above code-
class Answer {
private:
vector<string> ch;
public:
void setAns(string ans) { ch.push_back(ans); }
string getAns(int num) { return (ch[num]); }
int quantity() { return ch.size(); }
};
am i accessing elements out of bond? but i dont know where as i every number starts from 0 in programming
Yes you are.
while(i<=ch.a.quantity()){
should be
while(i<ch.a.quantity()){
Valid vector indexes are zero up to the size of the vector minus one. That should be obvious, if the valid indexes started at zero and went to the size of the vector then there would be one more valid index than the size of the vector, which makes no sense.
Generally you use a for loop for this kind of task
for (int i = 0; i < ch.a.quantity(); i++) {
a += ch.a.getAns(i);
}
It's a little easier to read that way.
I have written code for reading a text file containing 37000 DNA sequences and analyzing the sequences for specific pattern . But every time I run the code it says
codon.exe stopped working and Process returned 255 (0xff)
This is the code :
#include<iostream>
#include<vector>
#include<cstring>
#include<cstdio>
#include<fstream>
using namespace std;
int main()
{
ifstream dnafile;
dnafile.open("code.txt"); /// code.txt is notepad file name
if(!dnafile.is_open())
{
cout<<"file not opened";
}
int c=0;
vector <int> a;
vector <char> codon;
int l=0; /// lTH TERM OF DNA SEQUENCE
char x;
while((x = dnafile.get()) != EOF) /// READING CHARACTER BY CHARACER FROM FILE
{
if(x=='>')
{
l=0;
codon.push_back('#');
continue;
}
l++;
codon.push_back(x);
}
for(int l=0;l<codon.size();l++)
{
if(codon.at(l)=='#')
c++;
}
int c1[c+1];
float b[c+1],d[c+1];
for(int j=0;j<(c+1);j++)
{
for(int i=1;i<a.size();i++)
{
if (a[i]==0&&c1[j]!=0)
{
d[j]=(b[j]+a[i-c1[j]])/c1[j];
i++;
break;
}
else if(c1[j]==0)
d[j]=0;
else
{
b[j]=b[j]+(a[i]-a[i-1]);
}
}
continue;
}
for(int j=0,i=0;j<a.size(),i<(c+1);j=j+c1[i],i++)
{
cout<<"("<<d[i]<<","<<c1[i]<<","<<a[j]<<")"<<", ";
}
return 0;
}
Updated Code
Well I found two mistakes in it that you're making here and that's variable length array. You'd be getting an error on
int c1[c+1];
float b[c+1],d[c+1];
Update it to be a dynamic array like this, since c is a variable and is assigned a value at RunTime.
It'll only work if c is a const. For a variable you'd get C++ forbids variable length array
int *c1 = new int[c+1];
float *b = new float[c+1], *d = new float[c+1];
and don't forget to deallocate the memory in the end
delete [] c1;
delete [] b;
delete [] d;
Or you can use STL library as a workaround.
vector<int> or vector<float> would also work since they can update their size as you push elements into them
Also where you are checking your file existence
if(!dnafile.is_open())
{
cout<<"file not opened";
}
Add an else statement like this, since the code afterwards runs (in your implementation) even if the file is not found after printing "file not found"
else {
int c=0;
// all the code
delete [] c1;
delete [] b;
delete [] d;
}
return 0;
I am a newbie for OOP concepts and while trying to solve Project Euler Problem 7, to find 10001th prime number, I tried to do it using a class but encountered 2 major errors.
instantiating the class prime_n
initializing its argument
I have posted the code here for reference:
#include<iostream>
#include<cstdio>
using namespace std;
class prime_n
{
int j,k;
int n;
int *store;
public:
prime_n(int num)
{
n=num;
store[n];
}
static int isPrime(int j)
{
for(int i=2;i*i<=j;i++)
{
if(j%i==0) return 0;
}
return 1;
}
void find_n()
{
for(int i=0;i<n;i++)
{
store[i]=0;
}
store[0]=2;
j=3;
k=1;
while(store[n-1]==0)
{
if(isPrime(j)) store[k++]=j;
j+=2;
}
}
int get_num()
{
int value=store[n-1];
return value;
}
};
int main()
{
int num, req_num;
printf("Enter the position at which prime number is to be found ");
scanf("%d",&num);
printf("\nnumber = %d",num);
prime_n p = new prime_n(num);
req_num = p.get_num();
printf("The required prime number is %d\n",req_num);
return 0;
}
It would be a great help if someone could help me figure out where I am actually going wrong. Thanks a lot in advance!
Use
prime_n p(num);
or (not recommended in this particular case)
prime_n * p = new prime_n(num);
// some other code
req_num = p->get_num(); // note the -> operator replacing . in case of pointers
delete p;
The first case declares p on stack and it is automatically deallocated when the program leaves the scope (main function in this case)
The second one allocates space on heap and p is the pointer to it. You have to deallocate the memory manually.
As for your second question, the C++ way would be
#include <iostream>
...
int num;
std::cout << "Enter the position at which prime number is to be found "
std::cin >> num;
std::cout << std::endl << "Number = " << num << std::endl;
You provide a constructor:
prime_n(int num)
{
n=num;
store[n];
}
I think you are under the impression that store[n] creates an array with n elements, but that is not so; it attempts to access the (n+1)th element of an an array. Since store does not point anywhere (we are in the constructor, after all), the program crashes.
You probably want to write store = new int[num] instead.
And then I cannot see any call to find_n() originating from get_num() which is called in main(), so that your program would for now just return a random value.
This is the motivation behind the code. There is a boy named Bob and its his birthday today. He invites 50 friends over but not all of his friends want to buy him gifts. Bob is presented with 50 presents, though some of them are empty. His good friends tell him to close every 2nd box. For every third box, he is supposed to change every closed to open and every open to closed. He continues to do this for every n-th box where n is less than 50. The open boxes in the end will have the presents.
This is supposed to assist me in figuring out a problem for my math class, but I am not aware of all the complicated aspects of C++ programming. I want my string getValue(vector &arr) to return an array/vector. This code doesn't compile but it shows what I'm trying to do.
#include <iostream>
#include <vector>
#include<algorithm>
using namespace std;
string getValue(vector<string> &arr);
int main()
{
vector<string> myArr(2);
vector<string> newArr(2);
for(int i=2; i <= 50; i++)
{
if(i%2==0)
{
myArr.push_back("close");
}
else
{
myArr.push_back("open");
}
}
newArr = getValue(myArr);
for(int i=2; i <=50; i++)
{
cout << i << " " << newArr[i] << endl;
}
}
string getValue(vector<string> &arr)
{
for(int i=2; i <=50; i++)
{
if(arr[i]=="close")
{
arr[i]="open";
}
else if(arr[i]=="open")
{
arr[i]="close";
}
}
return arr;
}
You can't make your string getValue(vector<string> &arr) return an array/vector. It can only return a string. If you want a function to return an array/vector, then you have to say so in the function signature.
You're passing the vector into getValue() by reference, which means changes you make to it in that function will affect the original (in other words, you're not operating on a copy of the vector - you're actually operating on the vector).
So you don't need to return anything from getValue() - just make it void and it should do what you want.
string getValue(vector &arr) - the return type is string, not vector. You need to change its return type or set it to none.
PS:
newArr = getValue(myArr);
it's behind the SCOPE and it's wrongly positioned...
damn, third PS, wrong code rules are assigned
For the syntax part :-
The return type of the function is a string. Change it to vector for
your function to work properly.
You can simply declare the vectors globally. This will eliminate the
need to pass it to the function as well as return it.
For the logic part :-
Your question says that Bob toggles every third box but in your program Bob is changing every box to open if it is closed and every box to close if it is open. If what you wrote in the question is correct your code should be like this.
#include <iostream>
#include <vector>
using namespace std;
void getValue();
vector<string> myArr(2);
int main()
{
for(int i=2; i <= 50; i++)
{
if(i%2==0)
{
myArr.push_back("close");
}
else
{
myArr.push_back("open");
}
}
getValue();
for(int i=2; i <=50; i++)
{
cout << i << " " << myArr[i] << endl;
}
}
void getValue()
{
for(int i=3; i <=50; i+=3)
{
if(myArr[i]=="close")
{
myArr[i]="open";
}
else if(myArr[i]=="open")
{
myArr[i]="close";
}
}
}
Recently I do a exercise about algorithm with c++. Exercise in here:poj
I find two very confused questions.
I write a class MAZE and there are three primary functions in MAZE,they are
int left_path();int right_path();int mini_path();
and a function to print the answers:
void display(){
cout<<left_path()<<" "<<right_path()<<" ";
cout<<mini_path()<<endl;
}
the program can work correctly.As we see the function display() can be easy;
I write like this
void display(){
cout<<left_path()<<" "<<right_path()<<" "<<mini_path()<<endl;
}
just one change ;however the program can't work,it like loop infinitely.
following is the other question:
the function mini_path's frame like this
int maze::mini_path(){
ini();
queue<pair<int,int> > q;
q.push(make_pair(x,y));
while(!q.empty()){
pair<int,int> tmp=q.front();
q.pop();
int t=...;
if(E){
return t;
}
if(E){
S
}
if(E){
S
}
if(E){
S
}
if(E){
S
}
}
return -1;
}
if there is "return -1" in the end ,the function works right,else the function return random big number.
The program is in only one file and i use the gun compiler.
I don't show the total codes,because i think nobody wants to see them.I just want to ask what problems may lead above strange behaviors.
source code(simplified for question2):
typedef enum {LEFT=-1,RIGHT=1,UP,DOWN} direction;
ifstream fin("file_test3.txt");
class maze{
public:
maze(){input();}
int mini_path();
void input();
void display(){
cout<<mini_path()<<endl;
}
private:
bool is_not_dest(){
return !(x==d_x && y==d_y);
}
void ini_dir()
{
if(e_x==0) dir=DOWN;
else if(e_x==height-1) dir=UP;
else if(e_y==0) dir=RIGHT;
else dir=LEFT;
}
void ini(){
x=e_x;
y=e_y;
path_lenth=1;
ini_dir();
}
direction dir,d;
int width,height,maze_map[40][40],path_lenth;
int x,y,e_x,e_y,d_x,d_y;
};
void maze::input()
{
fin>>width>>height;
char sym;
for(int i=0;i<height;++i)
for(int j=0;j<width;++j){
fin>>sym;
if(sym=='#')
maze_map[i][j]=1;
else if(sym=='.')
maze_map[i][j]=0;
else if(sym=='S'){
maze_map[i][j]=-1;
e_x=i;
e_y=j;
}
else {
maze_map[i][j]=-2;
d_x=i;
d_y=j;
}
}
}
int maze::mini_path()
{
ini();
queue<pair<int,int> > q;
if(dir==LEFT) {maze_map[x][--y]=2;}
else if(dir==RIGHT) {maze_map[x][++y]=2;}
else if(dir==UP) {maze_map[--x][y]=2;}
else {maze_map[++x][y]=2;}
q.push(make_pair(x,y));
while(!q.empty()){
pair<int,int> tmp=q.front();
q.pop();
x=tmp.first;
y=tmp.second;
int t=maze_map[x][y]+1;
if((x==d_x && (y-d_y==1 || y-d_y==-1)) ||(y==d_y && (x-d_x==1||x-d_x==-1))){
return t;
}
if(maze_map[x-1][y]==0){
maze_map[x-1][y]=t;
q.push(make_pair(x-1,y));
}
if(maze_map[x+1][y]==0){
maze_map[x+1][y]=t;
q.push(make_pair(x+1,y));
}
if(maze_map[x][y-1]==0){
maze_map[x][y-1]=t;
q.push(make_pair(x,y-1));
}
if(maze_map[x][y+1]==0){
maze_map[x][y+1]=t;
q.push(make_pair(x,y+1));
}
}
return -1;
}
main()
{
int n;
fin>>n;
while(n-- >0){
class maze m;
m.display();
}
}
I see it! Can you see it? :)
#include <iostream>
using namespace std;
int foo(int bar)
{
cout << bar << endl;
return bar;
}
int _tmain(int argc, _TCHAR* argv[])
{
cout << foo(1) << foo(2) << foo(3) << endl;
return 0;
}
The output:
3
2
1
123
regarding question1:
The order in which the functions are called will be different.
the first solution will call them in following order:
right_path
left_path
mini_path
the second solution results in following order:
mini_path
right_path
left_path
so the solution you probaly want is:
void display(){
cout<<left_path()<<" ";
cout<<right_path()<<" ";
cout<<mini_path()<<endl;
}
There is not enough info to answer the first question; both codes are equivalent.
[Edit:Check other answers. Anyway, both codes should be equivalent: you have bugs in your code.]
About the second question, I guess that that "return -1" marks "no possible path" in your maze, that's why, when you remove it, your program stops working.
In the maze problem, a backtracking algorithm moves square by square. When from a square there is no possible path, this square must be marked as no path.