# Subarrays With K Different Integers Problem

## Description

LeetCode Problem 992.

Given an integer array nums and an integer k, return the number of good subarrays of nums.

A good array is an array where the number of different integers in that array is exactly k.

• For example, [1,2,3,1,2] has 3 different integers: 1, 2, and 3.

A subarray is a contiguous part of an array.

Example 1:

``````1
2
3
Input: nums = [1,2,1,2,3], k = 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:

``````1
2
3
Input: nums = [1,2,1,3,4], k = 3
Output: 3
Explanation: Subarrays formed with exactly 3 different integers: [1,2,1,3], [2,1,3], [1,3,4].
``````

Constraints:

• 1 <= nums.length <= 2 * 10^4
• 1 <= nums[i], k <= nums.length

## Sample C++ Code

``````1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
class Solution {
public:
int upToK(vector<int>& A, int K) {
int len = A.size();
unordered_map<int, int> m;
for (int i = 0; i < len; i ++) {
m[A[i]] = 0;
}

int cntdiff = 0;
int ans = 0;
int i = 0, j = 0;
while (j < len) {
m[A[j]] ++;
if (m[A[j]] == 1) cntdiff ++;

while (cntdiff > K) {
m[A[i]] --;
if (m[A[i]] == 0) cntdiff --;
i ++;
}

ans += j - i;
j ++;
}
return ans;
}

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