【HDOJ】2266 How Many Equations Can You Find

简单DFS。
 1 #include <cstdio>
 2 #include <cstring>
 3 
 4 #define MAXN 15
 5 
 6 char str[MAXN];
 7 __int64 x;
 8 int n;
 9 
10 void dfs(int s, __int64 v) {
11     int i;
12     __int64 tmp = 0;
13     if (str[s] == '') {
14         if (v == x)
15             ++n;
16         return ;
17     }
18 
19     for (i=s; str[i]; ++i) {
20         tmp = 10*tmp + str[i] - '0';
21         dfs(i+1, v+tmp);
22         if (s)
23             dfs(i+1, v-tmp);
24     }
25 }
26 
27 int main() {
28 
29     while (scanf("%s %I64d", str, &x) != EOF) {
30         n = 0;
31         dfs(0, 0);
32         printf("%d
", n);
33     }
34 
35     return 0;
36 }