How to implement recursive arrangement in java

Recursive arrangement

Recursive, commonly known as "I adjust myself", if understood from the perspective of data structure, it is actually a stack.

If we ask for the arrangement of A, B, and C, the process is roughly as follows:

(0) Initial state, no data in the stack. At this time, outside the stack: A, B, C

(1) Put A at the bottom of the stack. At this time, outside the stack: B, C

(2) Put B into the stack. At this time, outside the stack: C

(3) Put C into the stack. At this time, outside the stack: None, output the first arrangement ABC

(4) Pop C off the stack. At this time, outside the stack: C

(5) pops B off the stack. At this time, outside the stack: B, C

(6) Put C into the stack. At this time, outside the stack: B

(7) Put B into the stack. At this time, outside the stack: None, output the second arrangement ACB

, then pop back the stack in sequence, return to the initial state, then put B at the bottom of the stack, and repeat the action to get all arrangements.

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The example is as follows:

public class demo{
    public static void main(String[] args) {
        char buf[]={'A','B','C'}; //定义待排列数组
        perm(buf,0,buf.length-1);
    }
    public static void perm(char[] buf,int start,int end){
        if(start==end){//入栈结束条件，执行完该判断语句后开始逐步出栈
            for(int i=0;i<=end;i++){
                System.out.print(buf[i]);
            }
            System.out.println();
        }
        else{//递归正体
            for(int i=start;i<=end;i++){//控制入栈数据
                exchange(buf,start,i);//入栈操作
                perm(buf,start+1,end);//递归，对下一个数据执行出入栈操作
                exchange(buf,start,i);//出栈操作
            }
        }
    }
    public static void exchange(char[] c,int x,int y){ //交换数组中的数据，在栈里的表现就是入栈和出栈
        char temp=c[x];
        c[x]=c[y];
        c[y]=temp;
    }
}

Running result:

ABC
ACB
BAC
BCA
CBA
CAB

This article is written by java Zero Basic Introduction column recommendation, everyone is welcome to learn and communicate together!

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