打印字符串的所有排列

1：剑指offer,  通过递归，遍历到最底层开始打印。

package com.li.String;

/**
 * @program: GradleTestUseSubModule
 * @author: Yafei Li
 * @create: 2018-07-21 15:49
 * Java 中，怎么打印出一个字符串的所有排列
 **/
public class PrintStringSort {
    public static void main(String[] args){
        String str="abcd";
        char[] chars = str.toCharArray();
        int low=0;

        for (int i = 0; i <chars.length; i++) {
            char temp = chars[i];
            chars[i]=chars[0];
            chars[0]=temp;
            print(chars,low);
        }
    }

    private static void print(char[] chars, int low) {

        if (low == chars.length-1) {
            for (int i = 0; i < chars.length; i++) {
                System.out.print(chars[i]);
            }
            System.out.println("");
        }
        for (int i = low+1; i < chars.length; i++) {
            char temp=chars[i];
            chars[i] = chars[low+1];
            chars[low+1]=temp;

            print(chars,low + 1);

            char temp1=chars[i];
            chars[i] = chars[low+1];
            chars[low+1]=temp1;
        }
    }
}

结果：从后往前改变

abcd
abdc
acbd
acdb
adcb
adbc
bacd
badc
bcad
bcda
bdca
bdac
cabd
cadb
cbad
cbda
cdba
cdab
dabc
dacb
dbac
dbca
dcba
dcab

2:  打印一个字符串的字典排序，前面n个数相同，后面n个数相同，网易考试题。

package com.li.wangYi;

import java.util.LinkedHashSet;
import java.util.Set;

/**
 * @program: GradleTestUseSubModule
 * @author: Yafei Li
 * @create: 2018-07-21 15:49
 * Java 中，怎么打印出一个字符串的所有排列
 **/
public class Ques3 {
    static Set<String> set = new LinkedHashSet<>();
    public static void main(String[] args){
        String str="aaazzz";
        char[] chars = str.toCharArray();
        int low=0;

        for (int i = 0; i <chars.length; i++) {
            char temp = chars[i];
            chars[i]=chars[0];
            chars[0]=temp;
            print(chars,low);
        }

        for (String s : set) {
            System.out.println(s);
        }
    }

    private static void print(char[] chars, int low) {
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i < chars.length; i++) {
            stringBuffer.append(chars[i]);
        }
        set.add(stringBuffer.toString());
        stringBuffer=null;
for (int i = low+1; i < chars.length; i++) {
            char temp=chars[i];
            chars[i] = chars[low+1];
            chars[low+1]=temp;

            print(chars,low + 1);

            char temp1=chars[i];
            chars[i] = chars[low+1];
            chars[low+1]=temp1;
        }
    }
}

打印出aaazzz的字典顺序字符串，结果，从前往后改变。

aaazzz
aazazz
aazzaz
aazzza
azaazz
azazaz
azazza
azzaaz
azzaza
azzzaa
zaaazz
zaazaz
zaazza
zazaaz
zazaza
zazzaa
zzaaaz
zzaaza
zzazaa
zzzaaa

 3：打印字符串的所有排列

package com.li.zhongxing;


import java.io.InputStream;
import java.util.Scanner;

/**
 * a f g h b 能组成的含有3个字符的不同的组合的个数。
 */
public class Main2 {
    public static void main(String[] args){
        Main2 main1=new Main2();
        Class clazz = main1.getClass();
        InputStream Systemin = clazz.getResourceAsStream("/zhongxing/data2.txt");
        Scanner scanner = new Scanner(Systemin);

        char[] chars = {'a', 'd', 'r'};
        int index=0;
//        for (int j = 0; j < chars.length; j++) {
//            swap(chars,0, j);
            recursive(chars,index);
//        }
    }

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

    private static void recursive(char[] chars,int index){
        if (index == 3) {
            for (int i = 0; i < 3; i++) {
                System.out.print(chars[i]);
            }
            System.out.println("");
            return;
        }

        for (int i = index; i < chars.length; i++) {
            char temp = chars[i];
            chars[i]=chars[index];
            chars[index]=temp;

            recursive(chars,index+1);

            char temp1 = chars[i];
            chars[i]=chars[index];
            chars[index]=temp1;
        }
    }
}

结果：

adr
ard
dar
dra
rda
rad