Count Pairs in Two Arrays

class Solution {
public:
    long long countPairs(vector<int>& nums1, vector<int>& nums2) {
        int n = nums1.size();
        vector<int> d(n);
        for (int i = 0; i < n; ++i) d[i] = nums1[i] - nums2[i];
        sort(d.begin(), d.end());
        long long ans = 0;
        int l = 0, r = n - 1;
        while (l < r) {
            if (d[l] + d[r] > 0) {
                ans += r - l;
                --r;
            } else {
                ++l;
            }
        }
        return ans;
    }
};

import "sort"

func countPairs(nums1 []int, nums2 []int) int64 {
    n := len(nums1)
    d := make([]int, n)
    for i := 0; i < n; i++ {
        d[i] = nums1[i] - nums2[i]
    }
    sort.Ints(d)
    var ans int64
    l, r := 0, n-1
    for l < r {
        if d[l]+d[r] > 0 {
            ans += int64(r - l)
            r--
        } else {
            l++
        }
    }
    return ans
}

from typing import List

class Solution:
    def countPairs(self, nums1: List[int], nums2: List[int]) -> int:
        n = len(nums1)
        d = [nums1[i] - nums2[i] for i in range(n)]
        d.sort()
        ans = 0
        l, r = 0, n - 1
        while l < r:
            if d[l] + d[r] > 0:
                ans += r - l
                r -= 1
            else:
                l += 1
        return ans

function countPairs(nums1, nums2) {
    const n = nums1.length;
    const d = new Array(n);
    for (let i = 0; i < n; i++) d[i] = nums1[i] - nums2[i];
    d.sort((a, b) => a - b);
    let ans = 0;
    let l = 0, r = n - 1;
    while (l < r) {
        if (d[l] + d[r] > 0) {
            ans += r - l;
            r--;
        } else {
            l++;
        }
    }
    return ans;
}

class Solution {
    public long countPairs(int[] nums1, int[] nums2) {
        int n = nums1.length;
        int[] d = new int[n];
        for (int i = 0; i < n; i++) d[i] = nums1[i] - nums2[i];
        Arrays.sort(d);
        long ans = 0;
        int l = 0, r = n - 1;
        while (l < r) {
            if (d[l] + d[r] > 0) {
                ans += r - l;
                r--;
            } else {
                l++;
            }
        }
        return ans;
    }
}

function countPairs(nums1: number[], nums2: number[]): number {
    const n = nums1.length;
    const d: number[] = new Array(n);
    for (let i = 0; i < n; i++) d[i] = nums1[i] - nums2[i];
    d.sort((a, b) => a - b);
    let ans = 0;
    let l = 0, r = n - 1;
    while (l < r) {
        if (d[l] + d[r] > 0) {
            ans += r - l;
            r--;
        } else {
            l++;
        }
    }
    return ans;
}