全排列

package cn.hncu.search.dfs;

public class dfs {
    public static void main(String[] args) {
        char[] chs={'a','b','c','d'};
        int start=0;
        int end=chs.length-1;
        dfs(chs,start,end);
    }

    private static void dfs(char[] chs, int start, int end) {
        if(start==end+1){
            System.out.println(chs);
        }else{
            for(int i=start;i<=end;i++){
                swap(chs, start, i);
                dfs(chs, i+1, end);
                swap(chs, start, i);
            }
        }
    }

    private static void swap(char[] chs, int start, int i) {
        char temp=chs[start];
        chs[start]=chs[i];
        chs[i]=temp;
    } 

}