Codility code causes segmentation fault

Question

Here's my solution for Count Semiprimes codility problem, which is correct for small and medium inputs but results in segmentation fault for large test cases.

https://codility.com/demo/results/demo8JU794-FC7/

This normally happens with invalid pointers etc. however I can't see anything here which could cause such behaviour.

Are you able to spot anything wrong with the code?

vector<int> solution(int N, vector<int> &P, vector<int> &Q) {

    int M = P.size();

    // Use sieve of eratosthenes to find prime numbers within range 0 to N
    vector<int> sieve(N+1);
    sieve[0] = sieve[1] = 0;

    for (int i = 2; i <= N; ++i)
    {
        if (sieve[i] == 0)
        {
            int k = i * i;
            while(k <= N)
            {
                // For each non prime store its lowest prime divisor.
                sieve[k] = i;
                k += i;
            }
        }
    }

    vector<int> answer(M);

    for (int i = 0; i < M; ++i)
    {
        // Count semiprimes for each range (P[i], Q[i])
        int count = 0;

        for(int j = P[i]; j <= Q[i]; ++j)
        {
            // If a number is divisible by prime and the result of this division is also a prime
            // Then it's a semiprime.
            if (sieve[j] != 0 && sieve[j / sieve[j]] == 0)
            {
                count++;
            }
        }
        answer[i] = count;
    }

    return answer;
}

Answer 1

In this part, for N = 50000 the result of k = i * i overflows an int which is the reason for the segfault.

    if (sieve[i] == 0)
    {
        int k = i * i;
        while(k <= N)
        {
            // For each non prime store its lowest prime divisor.
            sieve[k] = i;
            k += i;
        }
    }

Answer 2

Can you post where the seg fault is at?

Just from the looks, sieve[0] = sieve[1] = 0; will exhibit undefined behavior when N is 0.