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 + 10;
const int INF = 0x3f3f3f3f;
int cnt[33];
char s[MAXN];

int main(void)        //Codeforces Round #297 (Div. 2) A. Vitaliy and Pie
{
    int n;
    while (scanf ("%d", &n) == 1)
    {
        scanf ("%s", s);    int len = strlen (s);
        memset (cnt, 0, sizeof (cnt));

        int ans = 0;
        for (int i=1; i<len; i+=2)
        {
            cnt[s[i-1]-'a']++;
            if (cnt[s[i]-'A'])    cnt[s[i]-'A']--;
            else    ans++;
        }

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

    return 0;
}


/*
3
aAbB
4
aBaCaB
5
xYyXzZaZ
*/