[HackerRank-pairs-again] Satisfactory Pairs

#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<string.h>
#include<vector>
using namespace std;
vector<int>o[310000];
int n;
const int maxn  =310000;
int vis[maxn];
int main()
{
cin>>n;
for(int i=1;i<=n;i++)
{
for(int j=1;j*j<=i;j++)
{
if(i%j==0)
{
o[i].push_back(j);
if(j*j!=i)
o[i].push_back(i/j);
}

}
sort(o[i].begin(),o[i].end());
}

memset(vis,0,sizeof(vis));
int sum =0 ;
for(int i=1;i<=n;i++)
{
for(int j=1;i*j<n;j++)
{
int g = n-i*j;
for(int k=0;k<o[g].size();k++)
{
if(o[g][k]>=i)break;
if(vis[o[g][k]]!=i)
{
vis[o[g][k]] = i;
sum++;
}
}
}
}
printf("%d\n",sum);

return 0;
}