为什么我在 HackerRank 上得到的输出与我的 IDE 输出不同？

Question

I am trying to solve a problem named "Jumping on the Clouds" on HackerRank.

I have written a code primarily and it gives the right output as my expectations. But when I am submitting the code on HackerRank it gives different output with the same input. How it is possible!

I tried to compile in different IDE and text editors like CodeBlocks, VSCode, and an online compiler(Ideone) and they give the correct output but HackerRank is showing a different output.

My code (C++):

#include <iostream>

using namespace std;

int main() {
  int n, count = 0;
  cin >> n;

  int arr[n];
  for(int i = 0; i < n; i++) {
    cin >> arr[i];
  }

  for(int i = 0; i < n; i++) {
    if(arr[i + 2] == 0) {
      count++;
      i = i + 1;
    } else if(arr[i + 1] == 0) {
      count++;
    } else {
      continue;
    }
  }

  cout << count << endl;

  return 0;
}

Outputs: Output on VSCode:

Output on Ideone:

Output on HackerRank:

Problem link: Jumping on the Clouds

Where is the problem and how to solve it?

Answer 1

Your code has undefined behavior because arr is accessed out of bounds. The loop constraint is i < n , but you access arr[i + 2] and arr[i + 1] .