You are given a sequence a consisting of n integers. Find the maximum possible value of (integer remainder of ai divided byaj), 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
3 3 4 5
output
2
给出 n 个数 a[0] ~ a[n-1] ,要你找出 a[i] % a[j] 最大.
处理一个数组x[i]表示 1~i 离i最近的数是什么。就可以过了。
#include <bits/stdc++.h>
usingnamespace std;
typedef longlong LL;
constint mod = (1e9+7);
constint N = 2000010;
bool num[N];
int x[N] , a;
int main()
{
int n ;
cin >> n ;
for( int i = 0 ; i < n ; ++i ) {
cin >> a;
num[a] = 1 ;
}
for( int i = 0 ; i <= 2e6 ; ++i ){
if( num[i] )x[i] = i ;
else x[i] = x[i-1] ;
}
int res = 0 ;
for( int i = 1 ; i <= 1e6 ; ++i ) if( num[i] ){
for( int j = 2 * i ; j <= 2e6 ; j += i ) {
res = max( res , ( x[j-1] ) % i );
}
}
cout << res << endl;
}
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