0992-subarrays-with-k-different-integers.adoc

992. Subarrays with K Different Integers

{leetcode}/problems/subarrays-with-k-different-integers/[LeetCode - Subarrays with K Different Integers^]

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 = [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: A = [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].

Note:

• 1 ⇐ A.length ⇐ 20000

• 1 ⇐ A[i] ⇐ A.length

• 1 ⇐ K ⇐ A.length

解题分析

解题中心思路是滑动窗口。

思考题

这个解题方案怎么理解？

参考资料

1. 面试官，你再问我滑动窗口问题试试？我有解题模板，不怕！

2. K 个不同整数的子数组 - K 个不同整数的子数组 - 力扣（LeetCode）

3. 仿照官方题解 提供更加清晰直观的解释 - K 个不同整数的子数组 - 力扣（LeetCode）

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 = [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: A = [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].

Note:

1. 1 ⇐ A.length ⇐ 20000

2. 1 ⇐ A[i] ⇐ A.length

3. 1 ⇐ K ⇐ A.length

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