[Codility] Caterpillar method : CountTriangles

https://app.codility.com/programmers/lessons/15-caterpillar_method/count_triangles/

CountTriangles coding task - Learn to Code - Codility

#include<algorithm>
// 1 2 5 8 10 12
int solution(vector<int> &A) {
    sort(A.begin(),A.end());
    int sz = A.size();
    int answer = 0;
    
    for(int i=0; i<sz-2; i++){
        int k = i +2;
        for(int j = i+1; j<sz; j++){
            while(k <sz && A[i] + A[j] > A[k]){
                k+=1;
            }
            if (k > j)
                answer += k - j - 1;
        }
    }
    return answer;
}