Safecracker

问题陈述：

　　杭州电子科技大学HANGZHOU DIANZI UNIVERSITY Online Judge Problem - 1015

问题解析：

　　深度优先搜索(Depth_First Search)

代码详解：　　

 #include <iostream>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>

 using namespace std;

 int flag, visited[];

 int cmp(const void *a, const void *b){
     return *(char *)b - *(char *)a;
 }

 int calculate(char *ans) {
     int res = , x = , sign = ;
     for(int i=; i<; i++) {
         for(int j=; j<=i; j++) {
             x *= (ans[i] - 'A' + );
         }
         res += x * sign;
         x = ;
         sign *= (-);
     }
     return res;
 }

 void dfs(char *str, int target, char *ans, int depth, int len) {
     if(depth == ) {
         if(calculate(ans) == target)
             flag = ;
         return;
     }
     for(int i=; i<len; i++) {
         if(!visited[i]) {
             ans[depth] = str[i];
             visited[i] = ;
             dfs(str, target, ans, depth+, len);
             if(flag)
                 return;
             visited[i] = ;
         }
     }
 }

 int main()
 {
     int target;
     char ans[], str[];
     while(scanf("%d %s", &target, str)!=EOF && !(target== && strcmp(str, "END")==)) {
         memset(visited, , sizeof(visited));
         qsort(str, strlen(str), sizeof(char), cmp);
         flag = ;
         dfs(str, target, ans, , strlen(str));
         if(flag){
             ans[] = '\0';
             puts(ans);
         } else {
             puts("no solution");
         }
     }
     return ;
 }

参考博客：CSDN Kizuki

转载请注明出处：http://www.cnblogs.com/michaelwong/p/4315092.html