http://acm.hdu.edu.cn/showproblem.php?pid=3474单调队列，又是第一次使用，本人蒟蒻无比啊。。。
  hdu 3474
1 #include <cstdio>
2#include <iostream>
3#include <cmath>
4#include <complex>
5#include <algorithm>
6#include <cstring>
7#include <queue>
8using namespace std;
9
10const int maxn = 1000000 + 10;
11int Q[maxn<<1], sum[maxn<<1];
12char neck[maxn<<1];
13int vis[2][maxn];
14
15void solve( int n, int m, int v )
16 {
17 sum[0] = 0;
18 for( int i = 1; i < m; i++ )
19 sum[i] = sum[i-1] + ( neck[i] == 'C' ? 1 : -1 );
20 int head = 0, tail = 0;
21 for( int i = 0; i < m; i++ )
22  {
23 while( head < tail && sum[Q[tail-1]] >= sum[i] ) tail--;
24 Q[tail++] = i;
25 if( i >= n )
26 {
27 while( i - Q[head] >= n ) head++;
28 vis[v][i-n] = ( sum[i-n] <= sum[Q[head]] );
29 }
30 }
31 }
32
33int main(int argc, char *argv[])
34{
35 int t;
36 scanf("%d",&t);
37 for( int p = 1; p <= t; p++ )
38 {
39 scanf("%s",neck+1);
40 int n = strlen( neck + 1 );
41 int m = n * 2 + 1;
42 for( int i = 1; i <= n; i++ )
43 neck[i+n] = neck[i];
44 neck[m] = 0;
45 memset( vis, 0, sizeof( vis ) );
46 solve( n, m, 0 );
47 reverse( neck + 1, neck + m );
48 solve( n, m, 1 );
49 int ans = 0;
50 for( int i = 1; i <= n; i++ )
51 if( vis[0][i] || vis[1][n-i] ) ans ++;
52 printf("Case %d: %d\n",p,ans);
53 }
54 return 0;
55}
56
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