题目传送门
1 /*
2 题意：给出一系列读者出行的记录，+表示一个读者进入，-表示一个读者离开，可能之前已经有读者在图书馆
3 构造：now记录当前图书馆人数，sz记录最小的容量，in数组标记进去的读者，分情况讨论一下
4 */
5 /************************************************
6 * Author :Running_Time
7 * Created Time :2015-8-6 0:23:37
8 * File Name :B.cpp
9 ************************************************/
10
11 #include <cstdio>
12 #include <algorithm>
13 #include <iostream>
14 #include <sstream>
15 #include <cstring>
16 #include <cmath>
17 #include <string>
18 #include <vector>
19 #include <queue>
20 #include <deque>
21 #include <stack>
22 #include <list>
23 #include <map>
24 #include <set>
25 #include <bitset>
26 #include <cstdlib>
27 #include <ctime>
28 using namespace std;
29
30 #define lson l, mid, rt << 1
31 #define rson mid + 1, r, rt << 1 | 1
32 typedef long long ll;
33 const int MAXN = 1e6 + 10;
34 const int INF = 0x3f3f3f3f;
35 const int MOD = 1e9 + 7;
36 bool in[MAXN];
37
38 int main(void) { //Codeforces Round #Pi (Div. 2) B. Berland National Library
39 int n; scanf ("%d", &n);
40 memset (in, false, sizeof (in));
41 int now = 0, sz = 0;
42 for (int i=1; i<=n; ++i) {
43 char s[2]; int x; scanf ("%s%d", &s, &x);
44 if (s[0] == '+') {
45 now++; in[x] = true;
46 if (now > sz) sz++;
47 }
48 else if (s[0] == '-') {
49 if (now == 0) {
50 if (in[x]) in[x] = false;
51 sz++;
52 }
53 else {
54 if (!in[x]) { //是之前就进入图书馆的读者
55 sz++;
56 }
57 else {
58 in[x] = false; now--;
59 }
60 }
61 }
62 }
63
64 printf ("%d
", sz);
65
66 return 0;
67 }