2014
01-04

# How Many Equations Can You Find

Now give you an string which only contains 0, 1 ,2 ,3 ,4 ,5 ,6 ,7 ,8 ,9.You are asked to add the sign ‘+’ or ’-’ between the characters. Just like give you a string “12345”, you can work out a string “123+4-5”. Now give you an integer N, please tell me how many ways can you find to make the result of the string equal to N .You can only choose at most one sign between two adjacent characters.

Each case contains a string s and a number N . You may be sure the length of the string will not exceed 12 and the absolute value of N will not exceed 999999999999.

Each case contains a string s and a number N . You may be sure the length of the string will not exceed 12 and the absolute value of N will not exceed 999999999999.

123456789 3
21 1

18
1

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
__int64 num,n,len;
char str[15];
void DFS(__int64 x,__int64 sum)
{
if(x==len)
{
if(sum==n)

num++;
return ;

}
__int64 k=0;//核心的东东  短短的几句  却是指数级的搜索量啊
for(int i=x;i<len;i++)//这里刚开始写成了从0开始，哎合适能搜到头啊
{
k=k*10+str[i]-'0';
DFS(i+1,sum+k);
if(x!=0)//第一个数字前不能加“-”号
DFS(i+1,sum-k);
}
}

int main()
{
while(scanf("%s %I64d",str,&n)!=EOF)
{
len=strlen(str);
num=0;
DFS(0,0);
printf("%I64d\n",num);
}
return 0;
}