Maximum Value - CodeForces 484 B 水题

B. Maximum Value

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

You are given a sequence a consisting of n integers. Find the maximum possible value of  (integer remainder of ai divided by aj), where 1 ≤ i, j ≤ n and ai ≥ aj.

Input

The first line contains integer n — the length of the sequence (1 ≤ n ≤ 2·105).

The second line contains n space-separated integers ai (1 ≤ ai ≤ 106).

Output

Print the answer to the problem.

Sample test(s)

input

33 4 5

output

2

题意：找出ai%aj的值的最大值。

思路：排序后从小往大找，假设处理的是a，那么就找比a*2-1，a*3-1，a*4-1...小的最大值。

AC代码如下：

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>#include<cmath>using namespace std;typedef long long ll;int num[2000110],maxn=1000000;int main(){    int T,t,n,m,i,j,k,ans=0;    scanf("%d",&n);    for(i=1;i<=n;i++)    {        scanf("%d",&k);        num[k]=k;    }    for(i=1;i<=maxn*2+1;i++)       if(num[i]!=i)         num[i]=num[i-1];    for(i=2;i<=maxn;i++)       if(num[i]==i)       {           for(j=i*2;j<=maxn*2+1;j+=i)           {               if(num[j-1]>i)                 ans=max(ans,num[j-1]%i);           }       }    printf("%d\n",ans);}