CF - 782A. Andryusha and Socks 模拟

1.题目描述：

A. Andryusha and Socks time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output

Andryusha is an orderly boy and likes to keep things in their place.

Today he faced a problem to put his socks in the wardrobe. He has n distinct pairs of socks which are initially in a bag. The pairs are numbered from 1 to n. Andryusha wants to put paired socks together and put them in the wardrobe. He takes the socks one by one from the bag, and for each sock he looks whether the pair of this sock has been already took out of the bag, or not. If not (that means the pair of this sock is still in the bag), he puts the current socks on the table in front of him. Otherwise, he puts both socks from the pair to the wardrobe.

Andryusha remembers the order in which he took the socks from the bag. Can you tell him what is the maximum number of socks that were on the table at the same time?

Input

The first line contains the single integer n (1 ≤ n ≤ 105) — the number of sock pairs.

The second line contains 2n integers x1, x2, ..., x2n (1 ≤ xi ≤ n), which describe the order in which Andryusha took the socks from the bag. More precisely, xi means that the i-th sock Andryusha took out was from pair xi.

It is guaranteed that Andryusha took exactly two socks of each pair.

Output

Print single integer — the maximum number of socks that were on the table at the same time.

Examples input 1 1 1 output 1 input 3 2 1 1 3 2 3 output 2 Note

In the first example Andryusha took a sock from the first pair and put it on the table. Then he took the next sock which is from the first pair as well, so he immediately puts both socks to the wardrobe. Thus, at most one sock was on the table at the same time.

In the second example Andryusha behaved as follows:

Initially the table was empty, he took out a sock from pair 2 and put it on the table. Sock (2) was on the table. Andryusha took out a sock from pair 1 and put it on the table. Socks (1, 2) were on the table. Andryusha took out a sock from pair 1, and put this pair into the wardrobe. Sock (2) was on the table. Andryusha took out a sock from pair 3 and put it on the table. Socks (2, 3) were on the table. Andryusha took out a sock from pair 2, and put this pair into the wardrobe. Sock (3) was on the table. Andryusha took out a sock from pair 3 and put this pair into the wardrobe. Thus, at most two socks were on the table at the same time.

2.题意概述：

他有2n只袜子在行李箱里，把它们一一拿到桌子上来，袜子任何两双颜色互不相同，每当桌面上有一双对应袜子以后就把它们整理好放回柜子里，问你在这个过程中桌面上最多出现几只袜子

3.解题思路：

直接模拟放袜子过程，用一个set存袜子颜色，一旦当前拿出的袜子颜色在set中已经出现则说明这对袜子应该拿下桌面，维护一下集合里面最大值就行。

4.AC代码：

#include <bits/stdc++.h> #define INF 0x3f3f3f3f #define maxn 100100 #define N 1111 #define eps 1e-6 #define pi acos(-1.0) #define e exp(1.0) using namespace std; const int mod = 1e9 + 7; typedef long long ll; typedef unsigned long long ull; bool vis[maxn]; int main() { #ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin); freopen("out.txt", "w", stdout); long _begin_time = clock(); #endif int n; while (~scanf("%d", &n)) { memset(vis, false, sizeof(vis)); set<int> s; int ans = 0; for (int i = 0; i < 2 * n; i++) { int tmp; scanf("%d", &tmp); if (!vis[tmp]) { s.insert(tmp); vis[tmp] = true; } else s.erase(tmp); ans = max(ans, (int)s.size()); } printf("%d\n", ans); } #ifndef ONLINE_JUDGE long _end_time = clock(); printf("time = %ld ms.", _end_time - _begin_time); #endif return 0; }