11_Number_good_pairs.cpp

// Given an array of integers nums, return the number of good pairs.
// A pair (i, j) is called good if nums[i] == nums[j] and i < j.

// Example 1:

// Input: nums = [1,2,3,1,1,3]
// Output: 4
// Explanation: There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed.
// Example 2:

// Input: nums = [1,1,1,1]
// Output: 6
// Explanation: Each pair in the array are good.
// Example 3:

// Input: nums = [1,2,3]
// Output: 0









// Optimal and easy looping solution

class Solution {
public:
    int numIdenticalPairs(vector<int>& nums) {
        int count = 0;
        for(int i = 0; i < nums.size(); i++){
            for(int j = i + 1; j < nums.size(); j++){
                if(nums[i] == nums[j]){
                    count++;
                }
            }
        }
        return count;
    }
};











// Mapping solution chatGPT 

class Solution {
public:
    int numIdenticalPairs(vector<int>& nums) {
        unordered_map<int, int> freq;
        int count = 0;

        for(int x : nums) {
            count += freq[x];  
            freq[x]++;
        }

        return count;
    }
};