LeetCode 976. Largest Perimeter Triangle

考点	难度
Sorting	Easy

题目

Given an integer array nums, return the largest perimeter of a triangle with a non-zero area, formed from three of these lengths. If it is impossible to form any triangle of a non-zero area, return 0.

思路

三角形必须满足a+b>c。先对所有数排序，选最大的数作为c，第二个和第三个作为a和b，检查是否满足条件。如果不满足说明剩下的数里没有a和b能和这个c满足三角形条件，所以把所有数向前移动一位。

答案

public int largestPerimeter(int[] A) {
        Arrays.sort(A);
        for (int i = A.length - 3; i >= 0; --i)
            if (A[i] + A[i+1] > A[i+2])
                return A[i] + A[i+1] + A[i+2];
        return 0;
}