Function Run Fun 动态规划／记忆化搜索

下面代码用的是记忆化搜索的方式来避免无用递归求得答案。除此之外也可以用动态规划从0-20循环打表得出全部答案后直接查询。

import java.io.PrintWriter;
import java.util.Scanner;

public class Main{
    static Scanner input = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static int[][][] dp = new int[21][21][21];
    public static void main(String[] args){
        initail();
        while(input.hasNext()){
            int a = input.nextInt();
            int b = input.nextInt();
            int c = input.nextInt();
            if(a==-1&&b==-1&&c==-1)break;
            if(a<=0||b<=0||c<=0){
                out.println("w("+a+", "+b+", "+c+") = "+1);
            }else if(a>20||b>20||c>20){
                out.println("w("+a+", "+b+", "+c+") = "+dp[20][20][20]);
            }else{
                out.println("w("+a+", "+b+", "+c+") = "+dp[a][b][c]);
            }
        }
        out.close();
    }
    static void initail(){

        for(int i=0;i<=20;i++){
            for(int j=0;j<=20;j++){
                for(int k=0;k<=20;k++){
                    if(i==0||j==0||k==0){
                        dp[i][j][k] = 1;
                    }else if(i<j&&j<k){
                        dp[i][j][k] = -dp[i][j-1][k]+dp[i][j][k-1]+dp[i][j-1][k-1];
                    }else{
                        dp[i][j][k] = dp[i-1][j][k]+dp[i-1][j-1][k]+dp[i-1][j][k-1]-dp[i-1][j-1][k-1];
                    }
                }
            }
        }
    }
}