【HDOJ】2369 Broken Keyboard

 1 #include <cstdio>
 2 #include <cstring>
 3 
 4 int visit[130];
 5 char s[1000005];
 6 
 7 int main() {
 8     int n, len;
 9     int i, j, k, tmp, l;
10 
11     while (scanf("%d%*c", &n)!=EOF && n) {
12         gets(s+1);
13         memset(visit, 0, sizeof(visit));
14         len = tmp = 0;
15         for (i=k=1; s[i]; ++i) {
16             if (visit[s[i]] == 0) {
17                 ++tmp;
18                 if (tmp>n && i-k>len)
19                     len = i - k;
20                 while (tmp > n) {
21                     if (--visit[s[k]] == 0)
22                         --tmp;
23                     ++k;
24                 }
25             }
26             visit[s[i]]++;
27         }
28         if (i-k > len)
29             len = i - k;
30         printf("%d\n", len);
31     }
32 
33     return 0;
34 }