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.
InputEach 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.OutputThe 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题目大意就是 在一个在来两个数字之间添加+ — 或者不做处理 使他可以得到后一个数,并记录次数就好了
思路:DFS遍历每一种情况
#include<iostream>
#include<string >
using namespace std;
string a;
typedef long long ll;
ll n,ans;
void dfs(int row,int sum){
if(row==a.size())
{
if(sum==n)
ans++;
return ;
} ll t=;
for(int i=row;i<a.size();i++)
{
t=t*+a[i]-'';
dfs(i+,sum+t);
if(row==) continue ; //因为当row==0时 sum=0,如过加减号的话相当于在第一个数前边加负号,所以要跳过
dfs(i+,sum-t);
}
}int main()
{
while(cin>>a>>n){
ans=;
dfs(,);
cout<<ans<<endl;
}
return ;
}