字符串的组合

/**
 * 题目：输入一个字符串，输出该字符串中字符的所有组合。举个例子，如果输入
 * abc，它的组合有a、b、c、ab、ac、bc、abc。
 */

public class Launch
{
	public static void main(String ...args)
	{
		combination("abcd");	
	}

	public static void combination(String str)
	{
		int strLength;

		strLength = str.length();
		tmpArray = new char[strLength];

		for(int len = 1; len <= strLength; ++len)
		{
			tlen = len;
			getCombination(str, 0, len);
		}
	}

	private static void getCombination(String str, int index, int n)
	{
		int strLength = str.length();
	
		if(n == 0)
		{
			for(int i = tlen - 1; i >= 0; --i)
			{
				System.out.print(tmpArray[i]);
			}
			System.out.print(" ");
		}
		else
		{
			for(int i = index; i < strLength; ++i)
			{
				if(strLength - index < n)
					break ;

				tmpArray[n - 1] = str.charAt(i);
				getCombination(str, i + 1, n - 1);
			}
		}
	}

	private static int tlen;
	private static char tmpArray[];
}

运行结果: a b c d ab ac ad bc bd cd abc abd acd bcd abcd