DFS (123456789)

HDU 2266

https://vjudge.net/problem/18753/origin

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.

Input

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.

Output

The output contains one line for each data set : the number of ways you can find to make the equation.

Sample Input

123456789 3
21 1

Sample Output

18
1

题目大意：在给定的字符串中添加 ' + ' 或  ‘ - ’ 使得 结果为给定的数字；求添加的方式有多少种.

#include<iostream>
#include<string>
using namespace std;

int ans=0;
int len;
int sum;	
string s1;
void dfs(int tt,int id){
	if(id==len){
		if(tt==sum){
			ans++;	
		}
		return ;
	}
	
	long long temp=0;
	for(int i=id;i<len;i++){
		temp=temp*10 + s1[i]-'0';
		dfs(tt+temp,i+1);
		if(id){
			dfs(tt-temp,i+1);
		}
	}
}



int main(){

	cin>>s1>>sum;
	len=s1.size();
	dfs(0,0);
	cout<<ans<<endl;
	return 0;
}