半数集问题(Java)

Posted 2021-11-04 nuist__NJUPT

方法1：递归法

import java.util.Scanner;

public class HalfSet1 {
    public static int halfSet(int n){
        int count = 1 ;
        for(int i=1; i<=n/2; i++){
            count += halfSet(i) ;
        }
        return count ;
    }
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in) ;
        int n = input.nextInt() ;
        System.out.println(halfSet(n)) ;
    }
}

方法2：记忆性递归（提高效率）

import java.util.Scanner;

public class HalfSet1 {
    static int [] arr = new int [1000] ;
    public static int halfSet(int n){
        int count = 1 ;
        if(arr[n] > 0){ //有记忆，直接取
            return arr[n] ;
        }
        for(int i=1; i<=n/2; i++) {
            count += halfSet(i);
        }
        arr[n] = count ; //传递保存
            return count ;
    }
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in) ;
        int n = input.nextInt() ;
        System.out.println(halfSet(n)) ;
    }
}