Valid Triangle Number

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

import "sort"

func triangleNumber(nums []int) int {
    sort.Ints(nums)
    n, ans := len(nums), 0
    for k := n - 1; k >= 2; k-- {
        l, r := 0, k-1
        for l < r {
            if nums[l]+nums[r] > nums[k] {
                ans += r - l
                r--
            } else {
                l++
            }
        }
    }
    return ans
}

from typing import List

class Solution:
    def triangleNumber(self, nums: List[int]) -> int:
        nums.sort()
        n, ans = len(nums), 0
        for k in range(n - 1, 1, -1):
            l, r = 0, k - 1
            while l < r:
                if nums[l] + nums[r] > nums[k]:
                    ans += r - l
                    r -= 1
                else:
                    l += 1
        return ans

function triangleNumber(nums) {
    nums.sort((a, b) => a - b);
    const n = nums.length;
    let ans = 0;
    for (let k = n - 1; k >= 2; k--) {
        let l = 0, r = k - 1;
        while (l < r) {
            if (nums[l] + nums[r] > nums[k]) {
                ans += r - l;
                r--;
            } else {
                l++;
            }
        }
    }
    return ans;
}

class Solution {
    public int triangleNumber(int[] nums) {
        Arrays.sort(nums);
        int n = nums.length, ans = 0;
        for (int k = n - 1; k >= 2; k--) {
            int l = 0, r = k - 1;
            while (l < r) {
                if (nums[l] + nums[r] > nums[k]) {
                    ans += r - l;
                    r--;
                } else {
                    l++;
                }
            }
        }
        return ans;
    }
}

function triangleNumber(nums: number[]): number {
    nums.sort((a, b) => a - b);
    const n = nums.length;
    let ans = 0;
    for (let k = n - 1; k >= 2; k--) {
        let l = 0, r = k - 1;
        while (l < r) {
            if (nums[l] + nums[r] > nums[k]) {
                ans += r - l;
                r--;
            } else {
                l++;
            }
        }
    }
    return ans;
}