全排列(java)

dfs+visited

import java.util.Scanner;

public class Main {
  public static void dfs(int[] a, boolean[] vis, int[] tmp, int start){
    int len = a.length;
    if(start == len){
      if(tmp[0] == 0){
        return;		
      }else{
        for(int j : tmp){
          System.out.print(j + " ");
	}
	System.out.println();
      }
      }else{
        for(int i=0; i<len; i++){
	  if(!vis[i]){
	  tmp[start] = a[i];
	  vis[i] = true;
	  dfs(a, vis, tmp, start+1);
	  vis[i] = false;
        }
      }
    }
  }

  public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    String str = s.nextLine();
    String[] strs = str.split(" ");
    int a[] = new int[strs.length];
    for(int i=0; i<strs.length; i++){
      a[i] = Integer.parseInt(strs[i]);
    }	
    int [] tmp = new int[a.length];
    boolean [] vis = new boolean[a.length];
    dfs(a, vis, tmp, 0);
  }
}	

dfs+swap

import java.util.Scanner;

public class Main2 {
  public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    String str = s.nextLine();
    String[] strs = str.split(" ");
    int a[] = new int[strs.length];
    for(int i=0; i<strs.length; i++){
      a[i] = Integer.parseInt(strs[i]);
    }
    dfs(a, 0);
  }
	
  static void dfs(int a[], int start ){
    if(start == a.length){
      for(int i :a){
        System.out.print(i);
      }
      System.out.println();
      return;
    }	
    
    for(int i=start; i<a.length; i++){
      swap(a, i, start);
      dfs(a, start+1);
      swap(a, i, start);
    }
  }
	
  static void swap(int[] a, int  i, int j){
    int tmp = a[i];
    a[i] = a[j];
    a[j] = tmp;
  }
}