2049: [USACO 2024 US Open Contest Gold] Problem 1. Cowreography

文件提交:无需freopen 内存限制:256 MB 时间限制:2.000 S
评测方式:普通裁判 命题人:
提交:1 解决:1

题目描述

The cows have formed a dance team, and Farmer John is their choreographer! The team's latest and greatest dance involves N cows (2N106) standing in a line. Each move in the dance involves two cows, up to K positions apart (1K<N), gracefully jumping and landing in each other's position.

There are two types of cows in the line – Guernseys and Holsteins. As such, Farmer John has documented the dance as a sequence of length-N binary strings, where a 0 represents a Guernsey, a 1 represents a Holstein, and the overall string represents how the cows are arranged in the line.

Unfortunately, Farmer Nhoj (who choreographs for a rival team) has sabotaged the dance and erased all but the first and last binary strings! With a big competition quickly approaching, Farmer John must waste no time in reconstructing the dance.

Given these two binary strings, help Farmer John find the minimum number of moves in the dance!

输入

The first line contains N and K.

The second line contains the first binary string.

The third line contains the last binary string.

It is guaranteed that both binary strings contain the same number of ones.

输出

The minimum number of moves in the dance.

样例输入

4 1
0111
1110

样例输出

3

提示

One possible dance:

0111 -> 1011 -> 1101 -> 1110

SAMPLE INPUT:

5 2

11000

00011

SAMPLE OUTPUT:

3

One possible dance:

11000 -> 01100 -> 00110 -> 00011

SAMPLE INPUT:

5 4

11000

00011

SAMPLE OUTPUT:

2

One possible dance:

11000 -> 10010 -> 00011

SCORING:

  • Inputs 4-5: K=1
  • Inputs 6-7: Both strings have at most 8 ones.
  • Inputs 8-15: N5000
  • Inputs 16-23: No additional constraints.

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