title
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
solution
求有多少个可以组成三角形的
class Solution {
public:
int triangleNumber(vector<int>& nums) {
int count = 0;
int res = 0;
if(nums.size()<3) return count;
sort(nums.begin(), nums.end());
for (int i = 0; i < nums.size()-2; i++) {
int k = i + 2;
for (int j = i + 1; j < nums.size() - 1 && nums[i] != 0; j++) {
while (k < nums.size() && nums[i] + nums[j] > nums[k]) {
k++;
}
count += k - j - 1;
}
}
return count;
}
};