POJ 1579 Function Run Fun

递归+记忆化搜索。

//Memory  156K	
//time  0MS
#include <stdio.h>
#define inf 0
int f[21][21][21];
int w(int a ,int b ,int c)
{
       if(a <= 0 || b <= 0 || c <= 0)
		   return 1;
       else if(a > 20 || b > 20 || c > 20)
       {
            if(f[20][20][20] == inf)
                f[20][20][20] = w(20 ,20 ,20);
            return f[20][20][20];
       }
       else if(a < b && b < c)
       {
            if(f[a][b][c - 1] == inf) 
				f[a][b][c - 1] = w(a ,b ,c - 1);
            if(f[a][b - 1][c - 1] == inf) 
				f[a][b - 1][c - 1] = w(a ,b - 1 ,c - 1);
            if(f[a][b - 1][c] == inf) 
				f[a][b - 1][c] = w(a ,b - 1 ,c);
            return f[a][b][c - 1] + f[a][b - 1][c - 1] - f[a][b - 1][c];
       }
       else
       {
            if(f[a - 1][b][c] == inf)
				f[a - 1][b][c] = w(a - 1 ,b ,c);
            if(f[a - 1][b - 1][c] == inf) 
				f[a - 1][b - 1][c] = w(a - 1 ,b - 1 ,c);
            if(f[a - 1][b][c - 1] == inf)
				f[a - 1][b] [c - 1] = w(a - 1 ,b ,c - 1);
            if(f[a - 1][b - 1][c - 1] == inf) 
				f[a - 1][b - 1][c - 1] = w(a - 1 ,b - 1 ,c - 1);
            return f[a - 1][b][c] + f[a - 1][b - 1][c] + f[a - 1][b][c - 1] - f[a - 1][b - 1][c - 1];
       }
}
int main()
{
      int a ,b ,c;
	  while(scanf("%d %d %d",&a ,&b ,&c) && (a != -1 || b != -1 || c != -1))
      {
          for(int i = 0 ;i <= 20 ;i++)
			 for(int j = 0 ;j <= 20 ;j++)
				for(int k = 0 ;k <= 20 ;k++)
					f[i][j][k] = inf;
          printf("w(%d, %d, %d) = %d\n" ,a ,b ,c ,w(a ,b ,c));
      }
      return 0;
}