PKU 1221(UNIMODAL PALINDROMIC DECOMPOSITIONS)的动态规划解法(JAVA实现)

我没有区分清楚动态规划和递归的区别！下面dp是动态规划，dp1是递归，dp1会超时！

 

package problem1221;

import java.util.Scanner;

public class Main {
	private static final int MAXNUM = 300;
	private static long [][] mat = new long[MAXNUM][MAXNUM];
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		for(int i = 0; i < MAXNUM; i++)
		{
			for(int j = 0; j < MAXNUM; j++)
				mat[i][j] = -1;
		}
		
		Scanner  scanner = new Scanner(System.in);
		int val;
		while(true)
		{
			val = scanner.nextInt();
			if(val == 0)
				break;
			System.out.println(val + " " + solve(val));
		}
	}
	
	private static long solve(int val) {
		// TODO Auto-generated method stub
		return dp(val, 1);
	}
	
	private static long dp(int val, int below)
	{
		if(val == 0)
			return 1;
		else if(val < below)
			return 0;
		else if(val == below)
			return 1;
		else
		{
			if(mat[val][below] >= 0)
				return mat[val][below];
			else
			{
				long result = dp(val - 2 * below, below) + dp(val, below + 1);
				mat[val][below] = result;
				return result;
			}
		}			
	}
	
	private static long dp1(int val, int below)
	{
		if(mat[val][below] >= 0)
			return mat[val][below];
		
		long result = 0;
		if(val == 0)
			result = 1;
		else
		{
			if(below <= val)
				result++;
			
			while(true)
			{
				if(2 * below > val)
					break;
				result += dp1(val - 2 * below, below);
				below++;
			}
		}
		mat[val][below] = result;
		return result;
	}
}