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  • 611. Valid Triangle Number

    Given an array consists of non-negative integers, your task is to count the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle.

    Example 1:

    Input: [2,2,3,4]
    Output: 3
    Explanation:
    Valid combinations are: 
    2,3,4 (using the first 2)
    2,3,4 (using the second 2)
    2,2,3
    

     Note:

    1. The length of the given array won't exceed 1000.
    2. The integers in the given array are in the range of [0, 1000]. 

    找出满足组成三角形的三条边的个数

     思路:组成三角形条件是两条较短的边的和大于第三条边

     1     public int triangleNumber(int[] nums) {
     2         Arrays.sort(nums);
     3         int count = 0;
     4         for (int i = nums.length - 1; i >= 2; i--) {
     5             int left = 0, right = i - 1;
     6             while (left < right) {
     7                 if (nums[left] + nums[right] > nums[i]) { //最短的两条边之和大于最长的边nums[i]
     8                     count += right - left; //left后面的数字,都可以结合right构成三角形
     9                     right--;
    10                 } else {
    11                     left++;
    12                 }
    13             }
    14         }
    15         return count;
    16     }
     
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  • 原文地址:https://www.cnblogs.com/wzj4858/p/7678495.html
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