java-选数字-递归

╰+攻爆jí腚メ 2023-05-21 15:29 13阅读 0赞

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzY3MzE1Ng_size_16_color_FFFFFF_t_70]  
**Sample Input**  
4 2  
**Sample Output**  
1 2  
1 3  
1 4  
2 3  
2 4  
3 4

明明拿到时是挺简单的，为啥写的时候就各种问题出现！！唉菜菜菜啊！！！！

递归的意思，在做题前先套方法！！

import java.util.Scanner;
    import java.util.Vector;
    
    public class Main{
        
        static long a,b;
        public static void search(int i,Vector<Integer> vector){
        
            if (i>a){
        
                return;
            }
            if (vector.size()==b){
        
                for (int j = 0; j <vector.size() ; j++) {
        
                    System.out.print(vector.get(j)+" ");
                }
                System.out.println();
                return;
            }else {
        
                for (int j = i+1; j <=a ; j++) {
        
                    vector.add(j);
                    search(j,vector);
                    vector.remove(vector.indexOf(j));
                }
            }
        }
        public static void main(String[] args) {
        
            Scanner scanner=new Scanner(System.in);
            a=scanner.nextInt();
            b=scanner.nextInt();
            Vector<Integer> v=new Vector<>();
            for (int i = 1; i <=a ; i++) {
        
                v.clear();
                v.add(i);
                search(i,v);
            }
        }
    }

编译错误，感觉对的

import java.util.ArrayList;
    import java.util.Scanner;
    
    
    public class Main{
        
        static long a,b;
        public static void search(int i,ArrayList arrays){
        
            if (i>a){
        
                return;
            }
            if (arrays.size()==b){
        
                for (int j = 0; j <arrays.size() ; j++) {
        
                    System.out.print(arrays.get(j)+" ");
                }
                System.out.println();
                return;
            }else {
        
                for (int j = i+1; j <=a; j++) {
        
                    arrays.add(j);
                    search(j,arrays);
                    arrays.remove(arrays.indexOf(j));
                }
    
            }
    
    
    
    
        }
        public static void main(String[] args) {
        
            Scanner scanner=new Scanner(System.in);
            a=scanner.nextInt();
            b=scanner.nextInt();
            ArrayList arrays;
            for (int i = 1; i <=a ; i++) {
        
                arrays=new ArrayList();
                arrays.add(i);
                search(i,arrays);
            }
        }
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzY3MzE1Ng_size_16_color_FFFFFF_t_70]: /images/20230521/4507802896c944099a445766e1c666f9.png