51Nod 1127 最短的包含字符串 (尺取法)

 #include <iostream>
 #include <algorithm>
 #include <string>
 #include <cstring>

 #define INF 0xfffffff
 using namespace std;
 const int maxn = ;
 int a[maxn];

 bool is_ok(){
     for (int i = ; i < ; i++){
         if (!a[i])
             return false;
     }
     return true;
 }

 int main(){
     ios::sync_with_stdio(false);
     string s;
     cin >> s;
     memset(a, , sizeof(a));
     bool flag = true;
     a[s[] - 'A']++;
     int ans = INF;
     int l = ;
     for (int i = ; i < s.length(); i++){
         a[s[i] - 'A']++;
         while (is_ok())
         {
             ans = min(ans, i - l + );
             a[s[l++] - 'A']--;
         }
     }
     if (ans == INF){
         cout << "No Solution" << endl;
     }
     else
         cout << ans << endl;
     system("pause");
     return ;
 }