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;
}