Same as https://leetcode.com/problems/3sum-closest

Assume `a`

is the longest edge, `b`

and `c`

are shorter ones, to form a triangle, they need to satisfy `len(b) + len(c) > len(a)`

.

```
public class Solution {
public int triangleNumber(int[] nums) {
int result = 0;
if (nums.length < 3) return result;
Arrays.sort(nums);
for (int i = 2; i < nums.length; i++) {
int left = 0, right = i - 1;
while (left < right) {
if (nums[left] + nums[right] > nums[i]) {
result += (right - left);
right--;
}
else {
left++;
}
}
}
return result;
}
}
```