题目如下:
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 <= 10000
1 <= A[i] <= 10^6
解题思路:三角形的边长规则有两个,一是任意两边之和大于第三边,这里其实只要判断两个较短的边的边长和是否大于最长边即可;二是任意两边之差小于第三边。
代码如下:
class Solution(object): def largestPerimeter(self, A): """ :type A: List[int] :rtype: int """ res = 0 A.sort(reverse=True) for i in range(len(A)-2): if A[i] - A[i+1] < A[i+2] and A[i] < A[i+1] + A[i+2]: res = A[i] + A[i+1] + A[i+2] break return res