[leetcode]valid-triangle-number. 有效三角形的个数

. - 力扣（LeetCode）

class Solution {
public:int triangleNumber(vector<int>& nums) {int n = nums.size();sort(nums.begin(), nums.end());int ans = 0;for (int i = 0; i < n; ++i) {for (int j = i + 1; j < n; ++j) {int left = j + 1, right = n - 1, k = j;while (left <= right) {int mid = (left + right) / 2;if (nums[mid] < nums[i] + nums[j]) {k = mid;left = mid + 1;}else {right = mid - 1;}}ans += k - j;}}return ans;}
};