I'm trying to handle following programming exercise from my C++ book: "Write a function which takes a string as argument and returns a primitve hash-code, which is calculated by adding the values of all characters in the string."
My solution to this is:
#include <iostream>
#include <string>
#define clrscr() system("cls")
#define pause() system("pause")
using namespace std;
int hashc(char string[]);
int main()
{
char phrase[256];
cout << "This program converts any string into primitve hash-code." << "\n";
cout << "Input phrase: "; cin.getline(phrase, sizeof(phrase));
cout << "\n";
cout << "Hash-code for your phrase is: " << hashc(phrase) << "\n\n";
pause();
return(0);
}
int hashc(char string[])
{
int index;
int length;
int hash_value = 0;
length = strlen(string);
for(index = 0; index >= length; ++index)
{
hash_value = hash_value + string[index];
}
return(hash_value);
}
The problem is: the function always returns hash_value = 0 as it seems that it is skipping the for-loop. When I return length in the function it gives back the correct length of a given string (which is index >= length for index = 0). Therefore it should normally trigger the for-loop, shouldn't it? A little hint right here is greatly appreciated!
Cheers!
An idiomatic for-loop should look like this:
for(index = 0; index < length; ++index)
{
hash_value += string[index];
}
The key features are that the index starts at 0 (index = 0), the index is compared to the length with 'less-than' (index < length) and, as you have it, the index is incremented using pre-increment (++index).
for(index = 0; index < length; ++index)
You're never entering the loop at the moment, and no characters caused a segmentation fault on my system. It enters the loop in the only situation that it passes the condition (length >= index, i.e. 0 >= 0) and then loops until it attempts to access an illegal location, at which point the seg fault occurs.
Related
The purpose of this code is to insert an x in between repeating letters. For example, if I were to input "CoolBoolFallmoose", the output would be "CoxolBoxolFalxlmoxose".
The code is also supposed to make an even number of pairs of letters, so if there is an odd amount of characters, an x is added to the end of the string. An example for this would be if we had "ball", it would become "balxlx" to make even pairs: "ba" "lx" "lx".
This is the code I have so far:
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main(){
string cipher, plain, paired = "";
cout << "input plaintext(no spaces, lowercase):\n";
cin >> plain;
for (int i=0;i<plain.length();i++){
if (plain[i]==plain[i+1]){
plain.insert(i,'x');
}
paired[i]=paired[i];
cout<<paired[i];
}
if (paired.length() % 2!= 0){
paired=+'x';
}
cout<<paired<<endl;
return 0;
}
The output I get is just the same as my input, no "x" added in any place.
The issue I am having is, every time I try to use the append() or insert() function for strings, I get an error from my compiler, which is xCode. Is there another way to solve this code?
EDIT: The error says:
No matching member function to call for insert
It also comes up for append().
I don't really know what you wanted to do with this part:
paired[i]=paired[i];
cout<<paired[i];
but otherwise the logic is good. Here is my take on it, x is a counter:
#include <iostream>
#include <string>
using namespace std;
int main(){
string m,n;
int x = 0;
cout << "Input: " << endl;
getline(cin, m);
for(int i = 0;i < m.length();i++){
x++;
n = n + m[i];
if(m[i] == m[i+1]){
n = n + 'x';
x++;
}
}
if((x % 2) != 0){
n = n + 'x';
}
cout << n;
return 0;
}
If you look at the available overloads of std::string::insert(), you will see that your statement plain.insert(i,'x'); does not match any of them, hence the compiler error. The overloads that takes a single char require either:
an index and a count (you are omitting the count)
an iterator and an optional count
There is, however, a couple of overloads that take just an index and a value, but they require a const char* or a std::string, not a single char.
Also, paired[i]=paired[i]; is a no-op. Except in your case, since paired has a size() of 0 since you never append anything to paired, so actually any access to paired[...] is undefined behavior.
Try this instead:
#include <iostream>
#include <string>
using namespace std;
int main(){
string plain, paired;
cout << "input plaintext(no spaces, lowercase):\n";
cin >> plain;
paired = plain;
for (string::size_type i = 1; i < paired.size(); ++i){
if (paired[i] == paired[i-1]){
paired.insert(i, 1, 'x');
// or: paired.insert(paired.begin()+i, 'x');
// or: paired.insert(i, "x");
// or: paired.insert(i, string{'x'});
// or: paired.insert(paired.begin()+i, {'x'});
++i; // skip the x just inserted
}
}
if (paired.size() % 2 != 0){
paired += 'x';
}
cout << paired << endl;
return 0;
}
Demo
A couple of points
First, Although the string.insert function says it takes an int as its first argument it really wants an iterator in this case.
Second, you are inserting elements into your "plain" string which increases its length and you have plain.length within your loop so you create an infinite loop.
Third, insert inserts BEFORE the index so you need to add 1 to I.
The code below will work for your loop:
Int len = plain.length();
Int count = 0;
for (int i = 0; i < len + count; i++)
{
If (plain[i] == plain[i + 1])
{
plain.insert(plain.begin() + (i +1), 'X');
++count;
}
}
cout << plain;
And as, mentioned below, if you want to handle spaces you can use getline(cin, plain) instead of cin.
I tried reading other questions to find the answer to my question but I got tired of seeing the answer being in a different coding language. I want to change the amount of numbers in my random error code. I am genuinely new to this so please no rude comments.
#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main () {
int i,j[3];
srand( (unsigned)time( NULL ) );
I set the array for j to 3 so I could try and get a maximum of 3 numbers.
for( i = 0; i < 1; i++ ) {
j[3] = rand();
cout <<"Error code: " << j << endl;
}
return 0;
}
Here is where the error comes in, the output of the code only sends the variable address instead of the random number. I really need help with this before I could continue my project. Please help.
Edit: Variable address is "0x7ffc9b46ed5c"
I can assume you want to set an array of size 3 to random numbers.
I set the array for j to 3
j[3] = rand();
You're not doing that, you're setting the 4th element in your array j as a random number, which happens to be out of bounds and invokes undefined behavior.
cout <<"Error code: " << j << endl;
Outputs the address of the first element in array j. Not the whole array.
How i would do it:
#include <iostream>
#include <ctime>
using namespace std;
int main()
{
srand(time(NULL));
int j[3];
for (int i = 0; i < 3; ++i)
j[i] = rand(); //sets every index of the array to rand()
cout << "Error code: ";
for (int i = 0; i < 3; ++i)
cout << j[i] << '\n'; //outputs all values from the array
return 0;
}
When you declare an array of size 3 by int j[3] you can refer to the first value by j[0], second value by j[1], and the third value by j[2]. If you want to display every value from your array you can use a normal for loop (using j[i]) or a range based for loop:
for(int& i : j)
cout<<i; //this loop will display every component from your array
I am working on a program that has to do with arrays. I decided that the input the user provides to be a string to later being converted to an integer once it is determined it is one. This way the program wouldn't run into an error when words/letters are entered. The issue I am having is the conversion from string to int. I want to change that because later in the program I am going to search the array for a given value and display it and its placement in the array. This is the code I have thus far:
#include <stdio.h>
#include <iostream>
using namespace std;
//check if number or string
bool check_number(string str) {
for (int i = 0; i < str.length(); i++)
if (isdigit(str[i]) == false)
return false;
return true;
}
int main()
{
const int size = 9 ;
int x, UserInput[size], findMe;
string userInput[size];
cout << "Enter "<< size <<" numbers: ";
for (int x =0; x < size; x++)
{
cin >> userInput[x];
if (check_number(userInput[x]))
{//the string is an int
}
else
{//the string is not an int
cout<<userInput[x]<< " is a string." << "Please enter a number: ";
cin >> userInput[x];}
}
int i;
for (int i =0; i < size; i++)
{
int UserInput[x] = std::stoi(userInput[x]); // error occurs here
}
for (int x= 0; x< size; x++)
{
if (UserInput = findMe)
{
cout <<"The number "<< UserInput[x] << "was found at " << x << "\n";
}
else
{
//want code to continue if the number the user is looking for isn't what is found
}
}
return 0;
}
Made comments here and there to kinda layout what I want the code to do and whatnot. I apperciate any help you can give, thank you.
This code:
int UserInput[x] = std::stoi(userInput[x]);
declares an int array of size x, to which you are assigning a single int (the result of std::stoi), which obviously doesn't work.
You need to assign an int to a particular index of the existing array, like this:
UserInput[x] = std::stoi(userInput[x]);
Given this comparison if (UserInput = findMe), which should actually be if (UserInput == findMe), it seems you want to declare a single int which stores the result of std::stoi. In that case, you should use a different name than the array, and write something like this:
int SingleUserInput = std::stoi(userInput[x]);
Also, please indent your code consistently, and compile with all your warnings turned on. Your code will be easier to read, and the compiler will point out additional problems with your code. And please don't use using namespace std;, it's a bad habit.
I don't understand why do u even need to use another loop to convert the string value to int. stdio.h header file does provides with preinstalled functions to make your work easier...
for (int x =0; x < size; x++)
{
getline(cin,userInput1[x]);
UserInput[x]=stoi(userInput1[x]);
}
stoi() function converts the string input to int, and you can call it dynamically as soon as you enter your string input,It will make you work easier and reduce the time complexity
I'm trying to write a program that creates and fills a vector with int values, then searches through it and returns the minimum value, recursively. I have the code written out and building, but it returns a weirdly large value for minimum every time- I have a feeling it's not properly assigning the smallest value to int minimum, but I'm not sure. Any thoughts?
#include <iostream>
#include <conio.h>
#include <vector>
using namespace std;
int vectorSize;
int minimum;
int result = -1;
int start;
int ending;
int answer;
int test;
int recursiveMinimum(vector<int>, int, int);
void main() {
cout << "How many values do you want your vector to be? ";
cin >> vectorSize;
cout << endl;
vector<int> searchVector(vectorSize);
start = 0;
ending = searchVector.size() - 1;
for (int i = 0; i < vectorSize; i++) {
cout << "Enter value for position " << i << " " << endl;
cin >> searchVector[i];
}
for (int x = 0; x < vectorSize; x++) {
cout << searchVector[x] << " ";
}
int answer = recursiveMinimum(searchVector, start, ending);
cout << "The smallest value in the vector is: " << answer;
_getch();
}
int recursiveMinimum(vector<int> searchVector, int start, int end) {
if (start < end) {
if (searchVector[start] < minimum) {
minimum = searchVector[start]; //this part seems to not work
}
start++;
recursiveMinimum(searchVector, start, end);
}
else {
return minimum;
}
}
`
Your minimum variable is not initialised, which leads to undefined behaviour. It should be set to the first value in the vector:
minimum = searchVector[0];
int answer = recursiveMinimum(searchVector, start, ending);
Additionally, ending is off by one, which makes it pick 6 as the smallest value out of [6, 9, 8, 4].
So, ultimately, your code should look like this:
minimum = searchVector[0];
int answer = recursiveMinimum(searchVector, start, ending + 1); // note the + 1
While irrelevant to the question, I advise you to use a tail call in recursiveMinimum, as explained here:
start++;
return recursiveMinimum(searchVector, start, end);
The main issue is that you do not initialise minimum. Hence, comparison searchVector[start] < minimum might never become true, and minimum remains uninitialized.
As a quick fix, write int minimum = MAX_INT; instead of int minimum;. MAX_INT is the maximum positive integer value (defined in limits.h). So the values in your array will never be greater that this value, and your minimum search loop will work (unless there are other issues; but for that, please consult the debugger :-) )
I am coding an assignment for my class where a user will input 10 letter answers, and the program will return a grade. I recently changed my char arrays to string arrays, because I think it makes it easier to read.
I went to debug my code and am now getting the error "Deubug Assertion Failed." I do not know what this means or how to fix it.
Any help would be appreciated.
Thanks!
Below is my code:
// Lab 8
// programmed by Elijah Barron
#include <iostream>
#include <string>
#include <iomanip>
using namespace std;
//Function headers
string inputAnswers(string given);
int numCorrect(string correctAnswers, string given);
int main()
{
string correctAnswers = "BCADBADCAB";
string given;
int numRight = 0;
inputAnswers(given);
numCorrect(correctAnswers, given);
double grade = 10 * numRight;
cout << "Your quiz grade is " << grade << "%" << endl;
return 0;
}
//Get the answers
string inputAnswers(string given)
{
for (int n = 0; n < 10; n++)
{
cout << "Please enter your answer for question #" << n + 1 << " ";
cin >> given[n];
}
return given;
}
//Find if answers are correct or incorrect
int numCorrect(string correctAnswers, string given)
{
int numRight = 10;
int n = 0;
for (int n = 0; n < 10; n++);
{
if (given[n] != correctAnswers[n])
numRight -= 1;
}
return numRight;
}
The immediate issue is that given will start off as an empty string as you haven't assigned it a value:
cin >> given[n];
is causing the assert failure because you're trying to change the first (second, third etc) character in a string with a length of zero. To fix the assert problem (but not the program, which will always return 0%), just initialise the string:
string given = "ZZZZZZZZZZ";
To fix the rest of the stuff (btw this isn't the only way):
Change:
string inputAnswers(string given); //for both prototype and function.
to:
void inputAnswers(string& given); //pass by reference instead of pass by value.
//also get rid of "return given;"
Change:
int n = 0; //the n here is different to the one in the next line
for (int n = 0; n < 10; n++); //this n's scope begins and ends here thanks to the semicolon
{//the code here is executed once, this isn't in the loop!
if (given[n] != correctAnswers[n]) //we're using the first n here, which is 0.
numRight -= 1;
}
to:
for (int n = 0; n < 10; n++) //only one n variable and no semicolon
{// now this is in the loop and will execute 10 times.
if (given[n] != correctAnswers[n])
numRight -= 1;
}
Don't bother with this line:
int numRight = 0; //Set at 0 and then never changed.
and change:
numCorrect(correctAnswers, given);
to:
int numRight = numCorrect(correctAnswers, given); //declared when necessary and assigned the correct value
You either want to reserve enough space in your vector to hold 10 characters, or use push_back to populate the vector. Indexing a vector with [] won't grow the vector for you.
EDIT:
Ignore the first part about reserve. That doesn't stop the debug assertion. You will want to change this
cin >> given[n];
To something like this:
char input;
cin >> input;
given.push_back(input);