（AC）Playlist

题目描述

You are given a playlist of a radio station since its establishment. The playlist has a total of n songs.
What is the longest sequence of successive songs where each song is unique?

输入

The first input line contains an integer n(1 ≤ n ≤ 2*105): the number of songs.
The next line has n integers k1,k2,...,kn(1 ≤ ki ≤ 109): the id number of each song.

输出

Print the length of the longest sequence of unique songs.

样例输入 Copy

8
1 2 1 3 2 7 4 2

样例输出 Copy

5

代码 

#include<bits/stdc++.h>
using namespace std;
int n,k[200009];
int main(){cin>>n;for(int i=0;i<n;++i)cin>>k[i];map<int,int>book;int ans=0,l=0,r=-1;for(int i=0;i<n;++i){if(book[k[i]]){ans=ans>(r-l+1)?ans:r-l+1;while(book[k[i]]&&l<=r){book[k[l]]--;l++;}}r++;book[k[i]]++;}ans=ans>(r-l+1)?ans:r-l+1;cout<<ans;return 0;
}