C++

1/**
2* Runtime: 4 ms, faster than 54.71%
3* Memory Usage: 7.5 MB, less than 56.34%
4*/
5class Solution {
6public:
7    int numIdenticalPairs(vector<int>& nums) {
8        int cnt = 0;
9        for (int i=0; i<nums.size(); ++i)
10        {
11            for (int j=i+1; j<nums.size(); ++j)
12            {
13                if (nums[i] == nums[j]) ++cnt;
14            }
15        }
16        
17        return cnt;
18    }
19};

JavaScript

1/**
2 * Runtime: 80 ms, faster than 47.12%.
3 * Memory Usage: 38.4 MB, less than 56.81%.
4 */
5var numIdenticalPairs = function(nums) {
6    let cnt = 0;
7    for(let i=0; i<nums.length; ++i) {
8        for(let j=i+1; j<nums.length; ++j) {
9            if (nums[i] == nums[j]) ++cnt;
10        }
11    }
12    return cnt;
13};

Ruby

1# Runtime: 48 ms, faster than 79.58%
2# Memory Usage: 209.7 MB, less than 70.42%
3def num_identical_pairs(nums)
4    cnt = 0
5    0.upto(nums.size-1) do |i|
6        (i+1).upto(nums.size-1) do |j|
7            if nums[i] == nums[j]
8                cnt += 1                
9            end
10        end
11    end
12    cnt
13end