Count the Number of Good Subarrays | Leetcode 2537

class Solution {
    using ll = long long;
public:
    long long countGood(vector<int>& nums, int k) {
        ll n = nums.size();
        ll left = 0, right = 0;
        ll good_subarrays = 0;
        unordered_map<ll,ll> freq;
        ll equal_pairs = 0; 

        while(left<n){
            while(right<n and equal_pairs<k){
                freq[nums[right]]++;
                if(freq[nums[right]]>=2)
                    equal_pairs += freq[nums[right]]-1;
                right++;
            }
            if(equal_pairs>=k)
                good_subarrays += n-right+1;

            //Remove left item
            freq[nums[left]]--;
            if(freq[nums[left]]>0)
                equal_pairs -= freq[nums[left]];
            left++;
        }
        return good_subarrays;
    }
};
/*
//JAVA
import java.util.HashMap;

class Solution {
    public long countGood(int[] nums, int k) {
        long n = nums.length;
        long left = 0, right = 0;
        long good_subarrays = 0;
        HashMap<Long, Long> freq = new HashMap<>();
        long equal_pairs = 0;

        while (left < n) {
            while (right < n && equal_pairs < k) {
                long num = nums[(int)right];
                freq.put(num, freq.getOrDefault(num, 0L) + 1);
                if (freq.get(num) >= 2) {
                    equal_pairs += freq.get(num) - 1;
                }
                right++;
            }
            if (equal_pairs >= k) {
                good_subarrays += n - right + 1;
            }

            // Remove left item
            long leftNum = nums[(int)left];
            freq.put(leftNum, freq.get(leftNum) - 1);
            if (freq.get(leftNum) > 0) {
                equal_pairs -= freq.get(leftNum);
            }
            left++;
        }
        return good_subarrays;
    }
}

#Python
from collections import defaultdict

class Solution:
    def countGood(self, nums: List[int], k: int) -> int:
        n = len(nums)
        left = 0
        right = 0
        good_subarrays = 0
        freq = defaultdict(int)
        equal_pairs = 0

        while left < n:
            while right < n and equal_pairs < k:
                freq[nums[right]] += 1
                if freq[nums[right]] >= 2:
                    equal_pairs += freq[nums[right]] - 1
                right += 1
            
            if equal_pairs >= k:
                good_subarrays += n - right + 1

            # Remove left item
            freq[nums[left]] -= 1
            if freq[nums[left]] > 0:
                equal_pairs -= freq[nums[left]]
            left += 1

        return good_subarrays
*/