How Many Equations Can You Find
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 892 Accepted Submission(s):
590
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 3
21 1
Sample Output
18
1
Author
dandelion
Source
Recommend
lcy
AC代码：
1 #include<cstring> 2 #include<cstdio> 3 using namespace std; 4 #define LL long long 5 LL num,n,len; 6 char str[15]; 7 void DFS(LL x, LL sum) 8 {//x是取的字符串的长度, sum是当前的值 9 if(x == len)//当取得字符串长度==字符串总串长度时 10 { 11 if(sum==n)//当前结果== n时 12 num++; 13 return ; 14 } 15 LL k=0; 16 for(int i=x;i<len;i++)/ 17 { 18 k=k*10+str[i]-'0'; 19 20 //加减两种可能 21 DFS(i+1, sum+k); 22 if(x != 0)//第一个数字前不能加“-”号 23 DFS(i+1, sum-k); 24 } 25 } 26 int main() 27 { 28 while(scanf("%s %lld",str,&n)!=EOF) 29 { 30 len=strlen(str); 31 num = 0; 32 DFS(0,0); 33 printf("%lld ", num); 34 } 35 return 0; 36 }