992

class Solution {
public:

    int atMostK(vector<int>& A, int K){
        int ans = 0, n=A.size(), right, left;
        unordered_map<int, int> count;

        for(left=right=0; right<n; right++){
            if(!count[A[right]]++) K--;
            while(K < 0){
                if(--count[A[left]] == 0) K++;
                left++;
            }
            ans += (right-left+1);
        }
        return ans;
    }

    int subarraysWithKDistinct(vector<int>& A, int K) {
        return atMostK(A, K) - atMostK(A, K-1);
    }
};