Given an array A of positive integers, call a (contiguous, not necessarily distinct) subarray of A good if the number of different integers in that subarray is exactly K.
(For example, [1,2,3,1,2] has 3 different integers: 1, 2, and 3.)
Return the number of good subarrays of A.
Example 1:
Input: A = 2
Output: 7
Explanation: Subarrays formed with exactly 2 different integers: [1,2], [2,1], [1,2], [2,3], [1,2,1], [2,1,2], [1,2,1,2].
Example 2:
Input: A = 3
Output: 3
Explanation: Subarrays formed with exactly 3 different integers: [1,2,1,3], [2,1,3], [1,3,4].
Note:
1 <= A.length <= 200001 <= A[i] <= A.length1 <= K <= A.length
Runtime: 128 ms, faster than 100.00% of C++ online submissions for Subarrays with K Different Integers.
Memory Usage: 25 MB, less than 100.00% of C++ online submissions for Subarrays with K Different Integers.
class Solution { public: int subarraysWithKDistinct(vector<int>& A, int K) { return atMostK(A, K) - atMostK(A,K-1); } int atMostK(vector<int>& A, int K) { int i = 0,res = 0; unordered_map<int,int> mp; for(int j=0; j<A.size(); j++) { if(!mp[A[j]]++) K--; while(K<0){ if(!--mp[A[i]]) K++; i++; } res += j - i + 1; } return res; } };