2379. Minimum Recolors to Get K Consecutive Black Blocks

Easy

542

15

You are given a **0-indexed** string `blocks`

of length `n`

, where `blocks[i]`

is either `'W'`

or `'B'`

, representing the color of the `i`

block. The characters ^{th}`'W'`

and `'B'`

denote the colors white and black, respectively.

You are also given an integer `k`

, which is the desired number of **consecutive** black blocks.

In one operation, you can **recolor** a white block such that it becomes a black block.

Return* the minimum number of operations needed such that there is at least one occurrence of *

`k`

**Example 1:**

Input:blocks = "WBBWWBBWBW", k = 7Output:3Explanation:One way to achieve 7 consecutive black blocks is to recolor the 0th, 3rd, and 4th blocks so that blocks = "BBBBBBBWBW". It can be shown that there is no way to achieve 7 consecutive black blocks in less than 3 operations. Therefore, we return 3.

**Example 2:**

Input:blocks = "WBWBBBW", k = 2Output:0Explanation:No changes need to be made, since 2 consecutive black blocks already exist. Therefore, we return 0.

**Constraints:**

`n == blocks.length`

`1 <= n <= 100`

`blocks[i]`

is either`'W'`

or`'B'`

.`1 <= k <= n`

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