字符串组合与字符替换 [英] String Combinations With Character Replacement
问题描述
我想通过我以前没有见过的情景工作,很努力拿出一个算法来正确地实现这一点。我的问题的一部分是正确的术语朦胧的回忆。我相信我所需要的是标准的结合问题的变化,但我很可能会关闭在那里。
I am trying to work through a scenario I haven't seen before and am struggling to come up with an algorithm to implement this properly. Part of my problem is a hazy recollection of the proper terminology. I believe what I am needing is a variation of the standard "combination" problem, but I could well be off there.
场景
给出一个例子字符串100
(姑且称之为 X
),产生<$ C的所有组合$ C> X :交换了其中的一个 0
(零) 0
(小写O)。因此,对于简单的例子100
,我希望这样的输出:
The Scenario
Given an example string "100"
(let's call it x
), produce all combinations of x
that swap out one of those 0
(zero) characters for a o
(lower-case o). So, for the simple example of "100"
, I would expect this output:
-
100
-
10°
-
1O0
-
1OO
"100"
"10o"
"1o0"
"1oo"
这将需要支持不同长度的字符串与 0
字符人数不等,但假设永远不会有 0
的超过5个实例。
This would need to support varying length strings with varying numbers of 0
characters, but assume there would never be more than 5 instances of 0
.
我有这个非常简单的算法,对于工作我的样本100
但分崩离析为更长的东西/更复杂的:
I have this very simple algorithm that works for my sample of "100"
but falls apart for anything longer/more complicated:
public IEnumerable<string> Combinations(string input)
{
char[] buffer = new char[input.Length];
for(int i = 0; i != buffer.Length; ++i)
{
buffer[i] = input[i];
}
//return the original input
yield return new string(buffer);
//look for 0's and replace them
for(int i = 0; i != buffer.Length; ++i)
{
if (input[i] == '0')
{
buffer[i] = 'o';
yield return new string(buffer);
buffer[i] = '0';
}
}
//handle the replace-all scenario
yield return input.Replace("0", "o");
}
我有一种挥之不去的感觉,递归可能是我的朋友在这里,但我。努力弄清楚如何把条件逻辑我需要在这里
I have a nagging feeling that recursion could be my friend here, but I am struggling to figure out how to incorporate the conditional logic I need here.
推荐答案
您的猜测是正确的;递归是你的朋友对这一挑战。这里有一个简单的解决方案:
Your guess was correct; recursion is your friend for this challenge. Here is a simple solution:
public static IEnumerable<string> Combinations(string input)
{
int firstZero = input.IndexOf('0'); // Get index of first '0'
if (firstZero == -1) // Base case: no further combinations
return new string[] { input };
string prefix = input.Substring(0, firstZero); // Substring preceding '0'
string suffix = input.Substring(firstZero + 1); // Substring succeeding '0'
// e.g. Suppose input was "fr0d00"
// Prefix is "fr"; suffix is "d00"
// Recursion: Generate all combinations of suffix
// e.g. "d00", "d0o", "do0", "doo"
var recursiveCombinations = Combinations(suffix);
// Return sequence in which each string is a concatenation of the
// prefix, either '0' or 'o', and one of the recursively-found suffixes
return
from chr in "0o" // char sequence equivalent to: new [] { '0', 'o' }
from recSuffix in recursiveCombinations
select prefix + chr + recSuffix;
}
这篇关于字符串组合与字符替换的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!