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POJ 1579 Function Run Fun 记忆化搜索

2014-08-27 15:06:00.0 搜索 c++  
导读:DescriptionWe all love recursion! Don't we?Consider a three-parameter recursive function w(a, b, c):if a <= 0 or b <= 0 or c <= 0, then w(a, b, c) returns:1if a > 20 or b > 20 or c > 20, then w(a, b, ...。。。

Description

We all love recursion! Don't we?

Consider a three-parameter recursive function w(a, b, c):

if a <= 0 or b <= 0 or c <= 0, then w(a, b, c) returns:
1

if a > 20 or b > 20 or c > 20, then w(a, b, c) returns:
w(20, 20, 20)

if a < b and b < c, then w(a, b, c) returns:
w(a, b, c-1) + w(a, b-1, c-1) - w(a, b-1, c)

otherwise it returns:
w(a-1, b, c) + w(a-1, b-1, c) + w(a-1, b, c-1) - w(a-1, b-1, c-1)

This is an easy function to implement. The problem is, if implemented directly, for moderate values of a, b and c (for example, a = 15, b = 15, c = 15), the program takes hours to run because of the massive recursion.

Input

The input for your program will be a series of integer triples, one per line, until the end-of-file flag of -1 -1 -1. Using the above technique, you are to calculate w(a, b, c) efficiently and print the result.

Output

Print the value for w(a,b,c) for each triple.

Sample Input

1 1 12 2 210 4 650 50 50-1 7 18-1 -1 -1

Sample Output

w(1, 1, 1) = 2w(2, 2, 2) = 4w(10, 4, 6) = 523w(50, 50, 50) = 1048576w(-1, 7, 18) = 1按照题目要求去递归搜索   因为产生了大量的子递归(重复)  所以肯定会超时 所以需要用到 记忆化搜索 把每个递归的a,b,c值保存起来  下次即可直接使用      代码
#include#include#include#includeusing namespace std;int q[50][50][50];             //记忆化搜索 int recursive(int a,int b,int c){    if(a<=0||b<=0||c<=0)        return 1;    if(q[a][b][c]!=0)        return q[a][b][c];        //直接使用    else if(a>20||b>20||c>20)        return recursive(20,20,20);    else if(a>a>>b>>c)    {        memset(q,0,sizeof(q));        if(a==-1&&b==-1&&c==-1)            break;        s=recursive(a,b,c);        printf("w(%d, %d, %d) = %d\n",a,b,c,s);    }    return 0;}


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