HDU 4403 dfs

A very hard Aoshu problem

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1589    Accepted Submission(s): 1089

Problem Description

Aoshu is very popular among primary school students. It is mathematics, but much harder than ordinary mathematics for primary school students. Teacher Liu is an Aoshu teacher. He just comes out with a problem to test his students:

Given a serial of digits, you must put a '=' and none or some '+' between these digits and make an equation. Please find out how many equations you can get. For example, if the digits serial is "1212", you can get 2 equations, they are "12=12" and "1+2=1+2". Please note that the digits only include 1 to 9, and every '+' must have a digit on its left side and right side. For example, "+12=12", and "1++1=2" are illegal. Please note that "1+11=12" and "11+1=12" are different equations.

 

Input

There are several test cases. Each test case is a digit serial in a line. The length of a serial is at least 2 and no more than 15. The input ends with a line of "END".

 

Output

For each test case , output a integer in a line, indicating the number of equations you can get.

 

Sample Input

1212

12345666

1235

END

 

Sample Output

2 2 0

 

Source

2012 ACM/ICPC Asia Regional Jinhua Online

 题意：

最长是15的字符串，要求添加一个‘=’和若干个‘+’使等式成立的方案数

代码：

//字符串最长是15，纯暴力，两个dfs。
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
char ch[20];
int len,ans;
void dfs2(int R,int k,int l,int pre,int m,int sum){
    if(l>R){
        if(m+pre==sum&&k==0) ans++;
        return;
    }
    pre=pre*10+ch[l]-'0';
    if(k>0&&pre!=0&&l!=R) dfs2(R,k-1,l+1,0,m+pre,sum);
    dfs2(R,k,l+1,pre,m,sum);
}
void solve(int l,int sum){
    for(int k=0;k<=len-1-l;k++){
        dfs2(len-1,k,l,0,0,sum);
    }
}
void dfs1(int R,int k,int l,int pre,int m){
    if(l>R){
        if(k==0) solve(R+1,m+pre);
        return;
    }
    pre=pre*10+ch[l]-'0';
    if(k>0&&pre!=0&&l!=R) dfs1(R,k-1,l+1,0,m+pre);
    dfs1(R,k,l+1,pre,m);
}
int main()
{
    while(scanf("%s",ch)&&(strcmp(ch,"END")!=0)){
        len=strlen(ch);
        ans=0;
        for(int h=0;h<len-1;h++){
            for(int k=0;k<=h;k++){
                dfs1(h,k,0,0,0);
            }
        }
        printf("%d
",ans);
    }
    return 0;
}