CODEWITHSUNDEEP
c++stringsegmentation-fault
kevincgreen
kevincgreen

Reputation: 11

std::string append segmentation fault

I encounter the error below when solving the leetcode problem https://leetcode.com/problems/largest-number/.

terminate called after throwing an instance of 'std::length_error'
  what():  basic_string::_M_create

So I run a similar code down bellow locally and it gives me segmentation fault. (Btw, it can run without any issues when the vector size is smaller, like 10). I already read the solutions, so I know there is a better way to do solve this leetcode problem. I just wanna know the nuance of this segmentation fault.

#include <bits/stdc++.h>
using namespace std;

int main() {
  vector<string> arr(100, "0");

  sort(arr.begin(), arr.end(), [](string &x, string &y) {
    string a = x;
    string b = y;
    a.append(y);
    b.append(x);
    int n = a.length();
    for (int idx = 0; idx < n; ++idx) {
      if (a[idx] != b[idx]) 
        return a[idx] > b[idx]; 
    }
    return true;
  });
}

Upvotes: 0

Views: 402

Answers (1)

fabian
fabian

Reputation: 82461

The third parameter of std::sort needs to satisfy the Compare named requirement, but your lambda clearly violates the requirement of the relationship being antireflexive, i.e. for any a, comp(a, a) must yield false, passing the string "0" as both parameters results in both a and b being "00" before the loop and the loop completes without returning resulting in true instead of the required false.

Upvotes: 5

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