1.18英文题面翻译

描述

Flip game is played on a rectangular 4x4 field with two-sided pieces placed on each of its 16 squares. One side of each piece is white and the other one is black and each piece is lying either it's black or white side up. Each round you flip 3 to 5 pieces, thus changing the color of their upper side from black to white and vice versa. The pieces to be flipped are chosen every round according to the following rules:

1. Choose any one of the 16 pieces.
2. Flip the chosen piece and also all adjacent pieces to the left, to the right, to the top, and to the bottom of the chosen piece (if there are any).

Consider the following position as an example:

bwbw
wwww
bbwb
bwwb
Here "b" denotes pieces lying their black side up and "w" denotes pieces lying their white side up. If we choose to flip the 1st piece from the 3rd row (this choice is shown at the picture), then the field will become:

bwbw
bwww
wwwb
wwwb
The goal of the game is to flip either all pieces white side up or all pieces black side up. You are to write a program that will search for the minimum number of rounds needed to achieve this goal.

输入

The input consists of 4 lines with 4 characters "w" or "b" each that denote game field position.

输出

Write to the output file a single integer number - the minimum number of rounds needed to achieve the goal of the game from the given position. If the goal is initially achieved, then write 0. If it's impossible to achieve the goal, then write the word "Impossible" (without quotes).

 OpenJudge - 755:Flip Game

翻译

描述

翻转游戏是一种在4×4的矩形板上玩的游戏，矩形板的每个格子里都有一个两面的棋子。棋子一面是黑色，一面是白色，并且放在矩形板上时要么黑色面朝上，要么白色面朝上。每一回合你都可以将3到5个棋子从黑色翻转为白色，反之亦然。选择翻转的棋子时应符合以下规则：

1、从这16个中任意选择。

2、翻转选择的棋子以及它上下左右相邻的棋子（如果有的话）。

如下是一个例子：

bwbw

wwww

bbwb

bwwb

这里b代表黑色面朝上的棋子，w代表白色面朝上的棋子。如果我们选择第一列第三行的棋子（如图所示），那么矩形板上棋子的排布将会变成如下：

bwbw

bwww

wwwb

wwwb

这个游戏的最终目的是将所有棋子翻转为黑色面朝上或所有棋子白色面朝上。你需要编写一个程序来计算达成这一目的所需要的最小翻转次数。

输入

输入包括四行包含b或w的字符，代表当前棋子的状态。

输出

输出一个整数——达成这一目的所需要的最小翻转次数。如果开始时目的已经达成，输出0.如果目的不可能达成，则输出一个单词“Impossible”（没有引号）。