hdoj How Many Equations Can You Find【DFS】

How Many Equations Can You Find

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 709    Accepted Submission(s): 462

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

 

Author

dandelion

 

Source

HDU 8th Programming Contest Online 

用递归枚举所有情况，若满足条件，数目+1，最后输出即可

#include<stdio.h>#include<string.h>#include<math.h>#include<stdlib.h>#include<algorithm>using namespace std;__int64 n;int num,m,len;char s[15];void dfs(int x,__int64 ans){if(x==len){if(ans == n)num++;return ;}__int64 a = 0;for(int i = x; i < len; i++){a = a*10+s[i]-'0';dfs(i+1, a+ans);if(x!=0)dfs(i+1, ans-a);}} int main(){while(~scanf("%s",s)){scanf("%I64d",&n);len = strlen(s);num = 0;dfs(0,0);printf("%d\n",num);}return 0;}