LeetCode-in-Java
992. Subarrays with K Different Integers
Hard
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]has3different integers:1,2, and3.
A subarray is a contiguous part of an array.
Example 1:
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:
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 * 1041 <= nums[i], k <= nums.length
Solution
public class Solution {
public int subarraysWithKDistinct(int[] nums, int k) {
int res = 0;
int prefix = 0;
int[] cnt = new int[nums.length + 1];
int i = 0;
int j = 0;
int uniqueCount = 0;
while (i < nums.length) {
if (cnt[nums[i]]++ == 0) {
uniqueCount++;
}
if (uniqueCount > k) {
--cnt[nums[j++]];
prefix = 0;
uniqueCount--;
}
while (cnt[nums[j]] > 1) {
++prefix;
--cnt[nums[j++]];
}
if (uniqueCount == k) {
res += prefix + 1;
}
i++;
}
return res;
}
}