Codeforces Round #323 (Div. 2) D. Once Again... 乱搞+LIS
1 second
256 megabytes
standard input
standard output
You are given an array of positive integers a1, a2, ..., an × T of length n × T. We know that for any i > n it is true that ai = ai - n. Find the length of the longest non-decreasing sequence of the given array.
The first line contains two space-separated integers: n, T (1 ≤ n ≤ 100, 1 ≤ T ≤ 107). The second line contains n space-separated integers a1, a2, ..., an (1 ≤ ai ≤ 300).
Print a single number — the length of a sought sequence.
4 3
3 1 4 2
5
The array given in the sample looks like that: 3, 1, 4, 2, 3, 1, 4, 2, 3, 1, 4, 2. The elements in bold form the largest non-decreasing subsequence.
题意:给你一个序列n,有T个连续这样的序列,求最长不下降子序列的长度;
思路:发现T很大,n很小对吧,
显然中间肯定是有一段是连续的相同的数对吧;
开始想前面取一个LIS,最后取一个LIS,中间相同,数量最多的那个数;
这个做法错误,可能后面的前一个还能多取;
如果T<=n比较小,我们只需要暴力跑LIS即可;
现在讨论T>n的情况;
然后发现只有n个数,也就是说最后的LIS最多只有n段不同的数;
也就是说我们只需要拿出n段序列出来,跑LIS即可;
因为最多n段,然后取完n段,多余的可以从中间插入;
#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<iostream>
#include<cstdio>
#include<cmath>
#include<string>
#include<queue>
#include<algorithm>
#include<stack>
#include<cstring>
#include<vector>
#include<list>
#include<set>
#include<map>
using namespace std;
#define ll long long
#define pi (4*atan(1.0))
#define mk make_pair
#define eps 1e-7
#define bug(x) cout<<"bug"<<x<<endl;
const int N=1e5+,M=1e6+,inf=;
const ll INF=1e18+,mod=; /// 数组大小
int arr[N],ans[N],len;
int binary_search(int i)
{
int left,right,mid;
left=,right=len;
while(left<right)
{
mid = left+(right-left)/;
if(ans[mid]>arr[i]) right=mid;
else left=mid+;
}
return left;
}
int LIS(int p)
{
ans[] = arr[];
len=;
for(int i=; i<=p; ++i)
{
if(arr[i]>=ans[len])
ans[++len]=arr[i];
else
{
int pos=binary_search(i);
ans[pos] = arr[i];
}
}
return len;
}
int flag[N];
int main()
{
int n,T,maxx=;
scanf("%d%d",&n,&T);
for(int i=;i<=n;i++)
scanf("%d",&arr[i]),flag[arr[i]]++,maxx=max(maxx,flag[arr[i]]);
for(int i=;i<n;i++)
for(int j=;j<=n;j++)
arr[i*n+j]=arr[j];
if(n>=T)printf("%d\n",LIS(n*T));
else printf("%d\n",LIS(n*n)+maxx*(T-n));
return ;
}
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