Printing issue in vectors (CPP) in looping - c++

Question

I was working on a problem statement. For its implementation, I am using vectors.
#include <iostream>
#include <vector>
using namespace std;
int busRemaining(vector<vector<int>> &busStation) {
int answer=0;
for(int i=0; i<=busStation.size(); i++) {
for(int j=i+1; j<=busStation.size(); j++)
{
if((busStation[i][0] <= busStation[j][0]) && (busStation[i][1] >= busStation[j][0])) {
answer++;
}
}
}
return answer;
}
int main()
{
vector<vector<int>> v = {{2, 8},{6, 10},{12, 14},{12, 20}};
cout<<busRemaining(v);
return 0;
}
The issue I am facing is -> after I run the program nothing is printed on the console. I have initialized answer to 0, So I suggest even if my looping logic is wrong it should return 0 at least.

Answer 1

You are using the wrong condition for your for-loops. Vector's are zero-indexed, so you should use less-than instead of less-than-or-equal:
for (int i = 0; i < busStation.size(); i++)
^
|
here
and
for (int j = i + 1; j < busStation.size(); j++)
^
|
here
The reason your function does not return, is because you touch memory outside the vector, memory that might not be allocated by your program, which makes your program's behavior undefined, i.e. the behavior of your program depends on the compiler and the operating system you use.

Answer 2

I could problems in your code, you can not access busStation[busStation.size()] because that element does not exist. Try to fix that issue first.

Answer 3

As you can see, in both for loops you have put i<=busStation.size(); and j<=busStation.size();. It is giving out of range error and causing a runtime error. it should be < and not <=. I hope you know why is it so. And in the 2nd loop, you have used again busStation.size() which might cause an error if you are trying to iterate elements of individual vectors inside vectors. I have written this code just to fix errors. I don't know if it works as you want.
#include <iostream>
#include <vector>
using namespace std;
int busRemaining(vector<vector<int>> &busStation) {
int answer=0;
for(int i=0; i<busStation.size(); i++) {
for(int j=i+1; j<busStation[i].size(); j++)
{
if((busStation[i][0] <= busStation[j][0]) && (busStation[i][1] >= busStation[j][0])) {
answer++;
}
}
}
return answer;
}
int main()
{
vector<vector<int>> v = {{2, 8},{6, 10},{12, 14},{12, 20}};
cout<<busRemaining(v);
return 0;
}