你这个复杂度是 $O( n^2 )$的,你用了 map 也过不了
by Razer_System @ 2023-10-25 22:00:58
@[Razer_System](/user/766788) 二分怎么写??? 实在不会
by chenlixin123456 @ 2023-10-27 14:10:30
好吧,正解还是用 map
```cpp
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll a[200005];
map<ll,ll> mp;
int main(){
ll n,c,count=0;
cin>>n>>c;
for(int i=1;i<=n;i++){
cin>>a[i];
mp[a[i]]++;
}
for(int i=1;i<=n;i++){
count+=mp[a[i]-c];
}
cout<<count;
return 0;
}
```
by Razer_System @ 2023-10-27 22:20:12
收 到!!!!!
by chenlixin123456 @ 2023-11-02 20:38:20