poj1579记忆和剪枝或动态规划dp

#include <iostream>using namespace std;
//***********************常量定义*****************************
const int NUM = 22;
//*********************自定义数据结构*************************
//********************题目描述中的变量************************
//**********************算法中的变量**************************
int dp[NUM][NUM][NUM];bool visit[NUM][NUM][NUM];
//***********************算法实现*****************************/*//记忆化搜索 递归形式的实现int RecSolve( int a, int b, int c ){    if( a<=0 || b<=0 || c<=0 )    {        return 1;    }    if( a>20 || b>20 || c>20 )    {        return RecSolve( 20, 20, 20 );    }
    //先查找，看以前是否计算过    if( visit[a][b][c] )    {        return dp[a][b][c];    }
    visit[a][b][c] = true;    if( a<b && b<c )    {        return dp[a][b][c] = RecSolve(a, b, c-1) + RecSolve(a, b-1, c-1) - RecSolve(a, b-1, c);    }    else    {        return dp[a][b][c] = RecSolve(a-1, b, c) + RecSolve(a-1, b-1, c) + RecSolve(a-1, b, c-1) - RecSolve(a-1, b-1, c-1);    }}*///DP实现int DPSolve( int a, int b, int c ){    if( a<0 || b<0 || c<0 )    {        a = b = c = 0;    }    if( a>20 || b>20 || c>20 )    {        a = b = c = 20;    }
    //a ,b ,c可能为负，必须放在if( a<0 || b<0 || c<0 )之后    if( visit[a][b][c] )    {        return dp[a][b][c];    }
    int x, y, z;    for( z=0; z<=a; z++ )    {        for( x=0; x<=b; x++ )        {            for( y=0; y<=c; y++ )            {                if( z==0 || x==0 || y==0 )                {                    dp[z][x][y] = 1;                }                else if( z<x && x<y )                {                    dp[z][x][y] = dp[z][x][y-1] + dp[z][x-1][y-1] - dp[z][x-1][y];                }                else                {                    dp[z][x][y] = dp[z-1][x][y] + dp[z-1][x-1][y] + dp[z-1][x][y-1] - dp[z-1][x-1][y-1];                }                //visit是全局变量                //如果已经计算过，则设置标记                visit[z][x][y] = true;            }        }    }    return dp[a][b][c];}
//************************main函数****************************
int main(){    //freopen( "in.txt", "r", stdin );    memset( dp, 0, sizeof(dp) );    memset( visit, false, sizeof(visit) );
    int a, b, c;    while( cin >> a >> b >> c, !( a == -1 && b == -1 && c == -1 ) )    {        int ans = DPSolve( a, b, c );        cout << "w(" << a << ", " << b << ", " << c << ") = " << ans << endl;    }
    return 0;}