HDU2266How Many Equations Can You Find

How Many Equations Can You Find

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 641    Accepted Submission(s): 421

Problem Description

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 321 1

 

Sample Output

181

 

题目大意：给定一串数字，你在其中添加“+”或“-”得到给定的数字

深度优先搜索：两种一起搜

#include <cstdio>#include <iostream>#include <algorithm>#include <cstring>using namespace std;#define ll long longint len;char s[15];ll n,ans;void dfs(int sum,int id){    if(id==len)    {        if(sum==n)            ans++;        return;    }    ll tmp=0;    for(int i=id;i<len;i++)    {        tmp=tmp*10+(s[i]-'0');        dfs(sum+tmp,i+1);        if(id)            dfs(sum-tmp,i+1);    }}int main(){   while(~scanf("%s%I64d",s,&n))   {       ans=0;       len=strlen(s);       dfs(0,0);       printf("%I64d\n",ans);   }}