UVA The Blocks Problem

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这道题自己一直WA，转载一篇别人的。。。代码写的很漂亮，虽然有四种操作，但操作之间的是有联系的，所以几个函数可以重用，这点很好。。

题目如下：

The Blocks Problem

Background

Many areas of Computer Science use simple, abstract domains for both analytical and empirical studies. For example, an early AI study of planning and robotics (STRIPS) used a block world in which a robot arm performed tasks involving the manipulation of blocks.

In this problem you will model a simple block world under certain rules and constraints. Rather than determine how to achieve a specified state, you will ``program'' a robotic arm to respond to a limited set of commands.

The Problem

The problem is to parse a series of commands that instruct a robot arm in how to manipulate blocks that lie on a flat table. Initially there aren blocks on the table (numbered from 0 to n-1) with block b_i adjacent to blockb_i+1 for all $0 \leq i < n-1$ as shown in the diagram below:

$\begin{figure}\centering\setlength{\unitlength}{0.0125in} %\begin{picture}(2......raisebox{0pt}[0pt][0pt]{$\bullet\bullet \bullet$ }}}\end{picture}\end{figure}$ Figure: Initial Blocks World

The valid commands for the robot arm that manipulates blocks are:

move a onto b
where a and b are block numbers, puts block a onto blockb after returning any blocks that are stacked on top of blocks a andb to their initial positions.
move a over b
where a and b are block numbers, puts block a onto the top of the stack containing blockb, after returning any blocks that are stacked on top of block a to their initial positions.
pile a onto b
where a and b are block numbers, moves the pile of blocks consisting of blocka, and any blocks that are stacked above block a, onto block b. All blocks on top of block b are moved to their initial positions prior to the pile taking place. The blocks stacked above blocka retain their order when moved.
pile a over b
where a and b are block numbers, puts the pile of blocks consisting of blocka, and any blocks that are stacked above block a, onto the top of the stack containing blockb. The blocks stacked above block a retain their original order when moved.
quit
terminates manipulations in the block world.

Any command in which a = b or in which a and b are in the same stack of blocks is an illegal command. All illegal commands should be ignored and should have no affect on the configuration of blocks.

The Input

The input begins with an integer n on a line by itself representing the number of blocks in the block world. You may assume that 0 <n <25.

The number of blocks is followed by a sequence of block commands, one command per line. Your program should process all commands until thequit command is encountered.

You may assume that all commands will be of the form specified above. There will be no syntactically incorrect commands.

The Output

The output should consist of the final state of the blocks world. Each original block position numberedi ( $0 \leq i < n$ wheren is the number of blocks) should appear followed immediately by a colon. If there is at least a block on it, the colon must be followed by one space, followed by a list of blocks that appear stacked in that position with each block number separated from other block numbers by a space. Don't put any trailing spaces on a line.

There should be one line of output for each block position (i.e., n lines of output wheren is the integer on the first line of input).

Sample Input

10move 9 onto 1move 8 over 1move 7 over 1move 6 over 1pile 8 over 6pile 8 over 5move 2 over 1move 4 over 9quit

Sample Output

 0: 0 1: 1 9 2 4 2: 3: 3 4: 5: 5 8 7 6 6: 7: 8: 9:

别人的很漂亮的代码：

自己的一直WA的代码，虽然自己的测试用例全都正确orz,如果大神们能给一个错误的测试数据或指出哪里错了，感激不尽QAQ：

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