leetcode976. Largest Perimeter Triangle

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url:https://leetcode.com/problems/largest-perimeter-triangle/

description:

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.

demo:

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

思路：将数组进行排序，然后从大到小开始遍历，满足条件的就是最大的，否则返回0。

代码：

class Solution {
public:
    int largestPerimeter(vector<int>& A) {
        sort(A.begin(),A.end());
        int n = A.size();
        for(int i = n-3;i>=0;i--){
            if(A[i]+A[i+1]>A[i+2]){
                return A[i]+A[i+1]+A[i+2];
            }
        }
        return 0;
    }
};