## 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].

## Rust Solution

``````struct Solution;

impl Solution {
fn triangle_number(mut nums: Vec<i32>) -> i32 {
let mut res = 0;
let n = nums.len();
nums.sort_unstable();
for i in (2..n).rev() {
let mut l = 0;
let mut r = i - 1;
while l < r {
if nums[l] + nums[r] > nums[i] {
res += r - l;
r -= 1;
} else {
l += 1;
}
}
}
res as i32
}
}

#[test]
fn test() {
let nums = vec![2, 2, 3, 4];
let res = 3;
assert_eq!(Solution::triangle_number(nums), res);
}
``````

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