全排列Permutations

描述

Given a collection of numbers, return all possible permutations.
For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1]

代码

package com.lilei.myes.es.pack1107;

public class quanpailie {

	public static void main(String[] args) {
		char[] cs = new char[] { 'a', 'b', 'c','d' };

		pailie(cs, 0);

	}

	public static void pailie(char[] cs, int e) {

		if (e == cs.length) {
			System.out.println(new String(cs));
		} else {

			for (int i = e; i < cs.length; i++) {
				swap(cs, i, e);
				pailie(cs,  e + 1);
				swap(cs, i, e);

			}

		}
	}

	static void swap(char[] cs, int a, int b) {
		char tmp = cs[a];
		cs[a] = cs[b];
		cs[b] = tmp;
	}

}