题目
链接：https://leetcode.com/problems…
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:3 <= A.length <= 100001 <= A[i] <= 10^6
思路
一个面积不为空的三角形，那么必须要最小的两条边之和大于第三边，才能构成一个三角形。并且要周长最大。很容易想到，先对数据进行排序，从最大的开始进行筛选，像窗口一样，往左侧移动，一旦找到符合条件的三角形，就是面积最大的。
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;
}