模拟 Codeforces Round #297 (Div. 2) A. Vitaliy and Pie

题目传送门

 /*
     模拟：这就是一道模拟水题，看到标签是贪心，还以为错了呢
     题目倒是很长:)
 */
 #include <cstdio>
 #include <algorithm>
 #include <iostream>
 #include <algorithm>
 #include <cstring>
 using namespace std;

 const int MAXN = 2e5 + ;
 const int INF = 0x3f3f3f3f;
 int cnt[];
 char s[MAXN];

 int main(void)        //Codeforces Round #297 (Div. 2) A. Vitaliy and Pie
 {
     int n;
     while (scanf ("%d", &n) == )
     {
         scanf ("%s", s);    int len = strlen (s);
         memset (cnt, , sizeof (cnt));

         int ans = ;
         for (int i=; i<len; i+=)
         {
             cnt[s[i-]-'a']++;
             if (cnt[s[i]-'A'])    cnt[s[i]-'A']--;
             else    ans++;
         }

         printf ("%d\n", ans);
     }

     return ;
 }

 /*
 3
 aAbB
 4
 aBaCaB
 5
 xYyXzZaZ
 */