Program crashes when I try to input values - c++

Question

so I've got integers m and n in my program, once you input the values it should create an array with values from m to n (for example m = 1 and n = 10, it creates array q with values from 1 to 10). Then it looks in the array if there are any numbers that are equal to any two number summ that are squared (for example, in the array, number 5 is equal to 1 squared + 2 squared). The problem is when I try to input the first value it crashes, pretty sure the problem is in the function but can't seem to figure it out. Thanks
#include <iostream>
using namespace std;
int squared (int a, int b, int q[]){
while (a<=0 || b<=0){
cout <<"You can't input an integer that is 0 or below: ";
cin >>a;
cin >>b;
if (a>0 || b>0) break;
}
for (int p=0; p<b; p++){
for (int i=a ; i<b; i++){
q[p] = a;
}
}
for (int z=0; z<b; z++){
for (int x=0; x<b; x++){
for (int c=0; c<b; c++){
if (q[z] == (q[x] * q[x]) + (q[c] * q[c])){
int result= (q[x] * q[x]) + (q[c] * q[c]);
return result;
}
}
}
}
}
int main () {
int m,n;
int M[100];
cout <<"Input integers m un n: ";
cin >>m,n;
cout <<squared(m,n,M);
return 0;
}

Answer 1

Most likely it crashes because of this: cin >>m,n;, it should be cin >> m >> n;, else you use n uninitialized on the next line, thus getting undefined behaviour, e.g. crash.
What compiler are you using and with what flags, since this would trigger some warnings/errors at compile normally.

Answer 2

cin >> m, n; is incorrect which inputs only m which can be interpreted as:
(cin >> m), n; which means: cin, n; to correct it:
cin >> m >> n;
if(a > 0 || b > 0) break; is redundant because you check for this condition twice: once in while condition second inside while loop thus checking for the same condition is redundant because while breaks automatically if the condition succeeds (a or b is equal or smaller than 0).
you passed an array without passing its size, you are lucky if you set the first element 1 the any second value is equal to the size of array eg:
m = 1; n = 10; then the size is ten which is correct.
what about:
m = 7; n = 10; // now is size 10? it's only 3
to correct it pass the size eg:
m = 4; n = 8;
int size = 8 - 4;
cout << Squared(m, n, M, size);
also:
for (int p = 0; p < b; p++)
{
for (int i = a ; i < b; i++)
{
q[p] = a;
}
}
you are assigning the same value a to all elements of array and iterating doing the same thing in the nested-loop!!! it's likely to write:
int x = 0; x = 0;
so the condition of result inside squared will never succeed because the same value is never equal to its square. 4 = 4 * 4 is never reached
here is what you search for:
#include <iostream>
using namespace std;
// I only make squared search for the result not inputing m and n lik e in yours
int squared (int m, int n, int* M)
{
int result;
for(int i(0); i < n; i++)
for(int j(0); j < n; j++)
for(int k(0); k < n; k++)
if( (M[i] == ( (M[j] * M[j]) + (M[k] * M[k]) )) && j != k) // here to avoid comparing with the same index
{
cout << M[i] << " = (" << M[j] << "*" << M[j] << ") + (" << M[k] << "*" << M[k] << ")" << endl;
result = ( (M[j] * M[j]) + (M[k] * M[k]) );
cout << result << endl;
return result; // if success we return result
}
return -1; // otherwise we return -1 as a sign of error (no square yields in negative value)
}
int main ()
{
int n, m, size;
do
{
cout <<"m: ";
cin >> m;
cout << "n: ";
cin >> n;
if(n <= 0 || m <= 0)
cout <<"You can't input an integer that is 0 or below: ";
// also it's very important to check whether n is greater than m or not because if m == n or m > n then size will be negative and as you know no array has a negative nor 0 size
if(m >= n)
cout << "n must be greater than m!" << endl;
}while (m <= 0 || n <= 0 || m >= n);
size = n - m; // getting size of array assuming m can be any value
int* M = new int[n - m]; // allocating dynamic array
// inputting array as you asked
for(int i(0), j = m; i < size; i++, j++)
M[i] = j;
// checking the values of array elements
for(int i = 0; i < size; i++)
cout << M[i] << ", " ;
cout << endl;
// getting the result
cout << squared(m, n, M) << endl;
// cleaning
delete[] M;
return 0;
}