HDU 2262 回溯算法 递归枚举

View Code

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 #include<string.h>
 4 #include<math.h>
 5 #include<ctype.h> 
 6 
 7 int  len; 
 8 long n,num;
 9 char s[15]; 
10 void DFS(int t,long ans)
11 {
12     int i; 
13     if(t == len)
14     { 
15        if(ans == n) 
16           num++; 
17        return ; 
18     } 
19     else
20     { 
21       long k = 0L;
22       for(i= t; i<len; i++)
23       {
24          k = k*10+(s[i]-'0');
25          DFS(i+1,ans+k);
26          if(t != 0) DFS(i+1,ans-k);        
27       }
28     } 
29 }      
30 
31 int main() 
32 {               
33     while(scanf("%s",s) != EOF) 
34     {
35       len = strlen(s);                  
36       scanf("%lld",&n);                    
37       num = 0L;                    
38       DFS(0,0L);                                            
39       printf("%ld\n",num);  
40     } 
41    //system("pause"); 
42    return 0; 
43 }    
44