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CodeForces - 566F Clique in the Divisibility Graph
阅读量:5149 次
发布时间:2019-06-13

本文共 1973 字,大约阅读时间需要 6 分钟。

Discription

As you must know, the maximum clique problem in an arbitrary graph is NP-hard. Nevertheless, for some graphs of specific kinds it can be solved effectively.

Just in case, let us remind you that a clique in a non-directed graph is a subset of the vertices of a graph, such that any two vertices of this subset are connected by an edge. In particular, an empty set of vertexes and a set consisting of a single vertex, are cliques.

Let's define a divisibility graph for a set of positive integers A = {

a1, a2, ..., an}as follows. The vertices of the given graph are numbers from set A, and two numbers ai and aj (i ≠ j) are connected by an edge if and only if either ai is divisible by aj, or aj is divisible by ai.

You are given a set of non-negative integers A. Determine the size of a maximum clique in a divisibility graph for set A.

Input

The first line contains integer n (1 ≤ n ≤ 106), that sets the size of set A.

The second line contains n distinct positive integers a1, a2, ..., an (1 ≤ ai ≤ 106) — elements of subset A. The numbers in the line follow in the ascending order.

Output

Print a single number — the maximum size of a clique in a divisibility graph for set A.

Examples

Input
8 3 4 6 8 10 18 21 24
Output
3

Note

In the first sample test a clique of size 3 is, for example, a subset of vertexes {3, 6, 18}. A clique of a larger size doesn't exist in this graph.

 

 

    我们不妨把边看成有向的,当 a[i]|a[j] 时从 i 向 j 连边(要先把重复元素缩成一个点),这样我们发现随便一条链上的元素 都可以成为一个团,并且这是一个DAG。

    所以我们直接找最长链好了。

 

#include
#define ll long longusing namespace std;const int maxn=1000000;int n,cnt[maxn+5],f[maxn+5];inline int read(){ int x=0; char ch=getchar(); for(;!isdigit(ch);ch=getchar()); for(;isdigit(ch);ch=getchar()) x=x*10+ch-'0'; return x;}int main(){ n=read(); for(int i=1;i<=n;i++) cnt[read()]++; for(int i=maxn;i;i--){ for(int j=i;j<=maxn;j+=i) f[i]=max(f[i],f[j]); f[i]+=cnt[i]; } printf("%d\n",f[1]); return 0;}

  

转载于:https://www.cnblogs.com/JYYHH/p/8949819.html

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