#include<bits/stdc++.h>
using namespace std;
const int maxn=1000000;
int t[4*maxn],g[4*maxn];
int n,a[4*maxn],ans;
int main()
{
int i,j;
scanf("%d",&n);
for (i=1;i<=n;i++)
{
scanf("%d",&a[i]);
g[a[i]]=1;
}
for (i=1;i<n;i++)
{
for (j=i+1;j<=n;j++)
{
t[a[i]+a[j]]++;
}
}
for (i=1;i<=20000;i++)
{
if (t[i]>0&&g[i]) ans++;
}
printf("%d",ans);
return 0;
}
by yeshuo2018 @ 2018-10-16 19:22:14
希望更丰富的展现？使用Markdown
by 塔罗兰 @ 2018-10-16 19:22:20
@[尘封的你](/space/show?uid=91203)
这个可以a的
思路自己看吧
by yeshuo2018 @ 2018-10-16 19:22:42
@[yeshuo2018](/space/show?uid=122578) 谢谢
by 尘封的你 @ 2018-10-16 19:26:08
@[尘封的你](/space/show?uid=91203)
不客气
by yeshuo2018 @ 2018-10-16 19:26:41