CodeForces 701C They Are Everywhere （滑动窗口）

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 int dp[300];
 4 int main()
 5 {
 6     int n;
 7     string s;
 8     while(~scanf("%d",&n))
 9     {
10         cin>>s;
11         int sum=0;
12         memset(dp,0,sizeof(dp));
13         for(int i=0; i<n; i++)
14         {
15             if(!dp[s[i]])
16             {
17                 dp[s[i]]=1;
18                 ++sum;
19             }
20         }
21         int st,en,sum1,ans;
22         st=en=sum1=0;
23         ans=1<<30;
24         memset(dp,0,sizeof(dp));
25         while(st<n)
26         {
27             while(en<n&&sum!=sum1)
28             {
29                 if(dp[s[en]]==0)
30                 {
31                     sum1++;
32                 }
33                 dp[s[en++]]++;
34             }
35             if(sum==sum1)ans=min(ans,en-st);
36             if(--dp[s[st++]]==0)sum1--;
37         }
38         cout<<ans<<endl;
39     }
40     return 0;
41 }