2537. Count the Number of Good Subarrays
Given an integer array nums and an integer k, return the number of good subarrays of nums.
A subarray arr is good if it there are at least k pairs of indices (i, j) such that i < j and arr[i] == arr[j].
A subarray is a contiguous nonempty sequence of elements within an array.
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 class Solution { public: long long countGood(vector<int>& A, int k) { long long res = 0, l = 0, r = 0, n = A.size(), now = 0; unordered_map<long long, long long> freq; for(; r < n; r++) { now += freq[A[r]]; freq[A[r]] += 1; if(now >= k) { while(l < r) { long long cut = freq[A[l]]  1; if(now  cut >= k) { now = cut; freq[A[l]] = 1; l += 1; } else break; } res += l + 1; } } return res; } };
