ZOJ 1004 Anagrams by Stack

ZOJ Problem Set - 1004

Anagrams by Stack

Time Limit: 2 Seconds

Memory Limit: 65536 KB

How can anagrams result from sequences of stack operations?
There are two sequences of stack operators which can convert TROT
to TORT:

[
i i i i o o o o
i o i i o o i o
]

where i stands for Push and o stands for Pop. Your
program should, given pairs of words produce sequences of stack
operations which convert the first word to the second.

Input

The input will consist of several lines of input. The first line
of each pair of input lines is to be considered as a source word
(which does not include the end-of-line character). The second line
(again, not including the end-of-line character) of each pair is a
target word. The end of input is marked by end of file.

Output

For each input pair, your program should produce a sorted list
of valid sequences of i and o which produce the
target word from the source word. Each list should be delimited
by

[
]

and the sequences should be printed in "dictionary order". Within
each sequence, each i and o is followed by a single
space and each sequence is terminated by a new line.

Process

A stack is a data storage and retrieval structure permitting two
operations:

Push - to insert an item and

Pop - to retrieve the most recently pushed item
We will use the symbol i (in) for push and o (out)
for pop operations for an initially empty stack of characters.
Given an input word, some sequences of push and pop operations are
valid in that every character of the word is both pushed and
popped, and furthermore, no attempt is ever made to pop the empty
stack. For example, if the word FOO is input, then the
sequence:

i i o i o o	is valid, but
i i o	is not (it's too short), neither is
i i o o o i	(there's an illegal pop of an empty stack)

Valid sequences yield rearrangements of the letters in an input
word. For example, the input word FOO and the sequence i i o i
o o produce the anagram OOF. So also would the sequence i
i i o o o. You are to write a program to input pairs of words
and output all the valid sequences of i and o
which will produce the second member of each pair from the
first.

Sample Input

madam
adamm
bahama
bahama
long
short
eric
rice

Sample Output

[
i i i i o o o i o o
i i i i o o o o i o
i i o i o i o i o o
i i o i o i o o i o
]
[
i o i i i o o i i o o o
i o i i i o o o i o i o
i o i o i o i i i o o o
i o i o i o i o i o i o
][
][
i i o i o i o o
]

Source: Zhejiang University Local Contest
2001

源码（一）：



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源码（二）



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解题报告：

此题属于数据结构的栈的摸拟题，大意：一个串到另一个串，找出所有进栈出栈的所有情况。

解法一较为复杂，递归操作，算法思想：目标串从第一个开始，原串从后面向前找，找到与之相同的，（1）即前面的元素进栈，该相同元素退栈。（2）不对之进行操作，继续向前找。可以找出所有的情况

解法二思路较为清晰，深搜。并且使用stl，较为方便。每一个元素，操作，不行的话，回溯。