Question

Given an array A of positive lengths, return the largest perimeter of a triangle with non-zero area, formed from 3 of these lengths.

If it is impossible to form any triangle of non-zero area, return 0.

Example 1:

Input: [2,1,2] Output: 5

Example 2:

Input: [1,2,1] Output: 0

Example 3:

Input: [3,2,3,4] Output: 10

Example 4:

Input: [3,6,2,3] Output: 8

Note:

1. 3 <= A.length <= 10000
2. 1 <= A[i] <= 10^6

Difficulty:Easy

Category:Array, Math

Analyze

Solution

class Solution {
 public:
  int largestPerimeter(vector<int>& A) {
    sort(A.begin(), A.end(), greater<int>());
    for (int i = 2; i < A.size(); ++i) {
      if (A[i] + A[i - 1] > A[i - 2]) return A[i] + A[i - 1] + A[i - 2];
    }
    return 0;
  }
};