hdoj 5375 Gray Code

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5375

编码规则：tmp = XOR(gr[i],gr[i-1]);

算是找规律的题目吧，考虑？前后字符和？数目的奇偶性就可以了，一个小trick就是当碰到需要减的时候是减问号区间内最小的那个，

然后就是调试的问题：

字符串从数组第二位开始存放，scanf("%s",s+1);

当用到min和max的时候记得每次使用前要清空。

 1 #include<stdio.h>
 2 const int MAXN = 200010;
 3 int XOR( char a, char b){
 4     int aa, bb;
 5     aa = a - ‘0‘;
 6     bb = b - ‘0‘;
 7     return aa^bb;
 8 }
 9 int main(){
10     char gr[MAXN];
11     int num[MAXN];
12     int _min;           int T, N;
13     int tmp;            int cnt, sum;
14     int lft, rgt;       int TT = 0;
15     scanf("%d",&T);
16     while(T--){
17         scanf("%s",gr+1);
18         gr[0] = ‘0‘;
19         cnt = 0; sum = 0; N = 0;_min = 1000000;
20         while( gr[N] != ‘\0‘)
21             N++;
22         for(int i = 1; i < N; ++i){
23             scanf("%d",&num[i]);
24         }
25         gr[N]=‘0‘;
26         num[N] = 0;
27         N++;
28         for(int i = 1; i < N; ++i){
29             if( gr[i] != ‘?‘){
30                 tmp = XOR(gr[i],gr[i-1]);
31                 if(tmp){
32                     sum += num[i];
33                 }
34             }
35             else{
36                 cnt = 0;
37                 lft = gr[i-1];
38                 for(;i<N;++i){
39                     if(gr[i] != ‘?‘){
40                         if( num[i] < _min )
41                             _min = num[i];
42                         sum += num[i];
43                         break;
44                     }
45                     else{
46                         cnt++;
47                         sum += num[i];
48                         if( num[i] < _min )
49                             _min = num[i];
50                     }
51                 }
52                 rgt = gr[i];
53                 if(( ( lft != rgt) && ( cnt % 2 == 1))||( (lft == rgt) && (cnt % 2 == 0) )){
54                     sum = sum - _min;
55                 }
56                 _min = 1000000;
57             }
58         }
59         printf("Case #%d: %d\n",++TT,sum);
60     }
61 }