## Algorithm

Problem Name: 611. Valid Triangle Number

Given an integer array `nums`, return 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: nums = [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
```

Example 2:

```Input: nums = [4,2,3,4]
Output: 4
```

Constraints:

• `1 <= nums.length <= 1000`
• `0 <= nums[i] <= 1000`

## Code Examples

### #1 Code Example with C++ Programming

```Code - C++ Programming```

``````
class Solution {
public:
int triangleNumber(vector<int>& nums) {
sort(nums.begin(), nums.end());
int count = 0, n = nums.size();
for(int i = 0; i  <  n; i++)
for(int j = i + 1; j  <  n; j++)
for(int k = j + 1; k  <  n; k++)
if(nums[i] + nums[j] > nums[k]) count++;
return count;
}
};

class Solution {
public:
int triangleNumber(vector<int>& nums) {
sort(nums.begin(), nums.end());
int count = 0, n = nums.size();
for(int i = n - 1; i > 1; --i) {
int l = 0, r = i - 1;
while (l < r> {
if (nums[l] + nums[r] > nums[i]) {
count += r - l;
--r;
} else {
++l;
}
}
}
return count;
}
};
``````
Copy The Code &

Input

cmd
nums = [2,2,3,4]

Output

cmd
3

### #2 Code Example with Java Programming

```Code - Java Programming```

``````
class Solution {
public int triangleNumber(int[] nums) {
Arrays.sort(nums);
int count = 0;
for (int i=0;i < nums.length-2;i++) {
int k = i+2;
for (int j=i+1;j < nums.length-1 && nums[i] != 0; j++) {
while(k < nums.length && nums[k] < nums[i] + nums[j])
k++;
count += k-j-1;
}
}

return count;
}
}
``````
Copy The Code &

Input

cmd
nums = [2,2,3,4]

Output

cmd
3

### #3 Code Example with Javascript Programming

```Code - Javascript Programming```

``````
const triangleNumber = function(nums) {
nums.sort((a, b) => a - b);
let count = 0;
let n = nums.length;
for (let i = n - 1; i >= 2; i--) {
let lo = 0;
let mid = i - 1;
while (lo  <  mid) {
if (nums[lo] + nums[mid] > nums[i]) {
count += mid - lo;
mid -= 1;
} else {
lo += 1;
}
}
}
return count;
};

console.log(triangleNumber([2, 2, 3, 4]));
``````
Copy The Code &

Input

cmd
nums = [4,2,3,4]

Output

cmd
4