[Codility] Lesson 6 - Triangle

Task discription

An array A consisting of N integers is given. A triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

• A[P] + A[Q] > A[R],
• A[Q] + A[R] > A[P],
• A[R] + A[P] > A[Q].

For example, consider array A such that:

A[0] = 10    A[1] = 2    A[2] = 5
A[3] = 1     A[4] = 8    A[5] = 20

Triplet (0, 2, 4) is triangular.

Write a function:

class Solution { public int solution(int[] A); }

that, given an array A consisting of N integers, returns 1 if there exists a triangular triplet for this array and returns 0 otherwise.

For example, given array A such that:

A[0] = 10    A[1] = 2    A[2] = 5
A[3] = 1     A[4] = 8    A[5] = 20

the function should return 1, as explained above. Given array A such that:

A[0] = 10    A[1] = 50    A[2] = 5
A[3] = 1

the function should return 0.

Write an efficient algorithm for the following assumptions:

• N is an integer within the range [0..100,000];
• each element of array A is an integer within the range [−2,147,483,648..2,147,483,647].

Source code

#include <algorithm>
#include <vector>

using namespace std;

int solution(vector<int> &A) {
    sort(A.begin(), A.end());

    if(A.size() < 3) return 0;

    for (int i=0;i<A.size()-2;i++) {
        if ((long long)A[i+1] + A[i] > (long long)A[i+2]) {
            return 1;
        }
    }

    return 0;
}

Review

이 문제도 Overflow 발생을 막기 위해 long long 타입으로 처리해줘야 했다.
문제풀 때 범위를 주의깊게 봐야겠다..💦