Submission #522963

#	Time	Username	Problem	Language	Result	Execution time	Memory
522963		TheKingAleks	Star triangles (IZhO11_triangle)	C++14	100 / 100	164 ms	11808 KiB

triangle

#include<bits/stdc++.h>
using namespace std;
const int MAX_N = 3e5+2;
pair<int,int> a[MAX_N];
unordered_map<int,int> on_y;
unordered_map<int,int> on_x_res;
bool cmp(pair<int,int> e1, pair<int,int> e2)
{
    if(e1.second == e2.second) return e1.first < e2.first;
    return e1.second < e2.second;
}
int ans = 0;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int n,x0,y0;
    cin>>n;
    for(int i=0; i<n; i++)
    {
        cin>>x0>>y0;
        a[i] = {x0,y0};
        on_y[y0]++;
    }
    sort(a,a+n,cmp);
    for(int i=0; i<n; i++)
    {
        if(on_x_res.find(a[i].first) != on_x_res.end()) ans += on_x_res[a[i].first];
        on_x_res[a[i].first] += on_y[a[i].second]-1;
    }
    on_x_res.clear();
    for(int i=n-1; i>=0; i--)
    {
        if(on_x_res.find(a[i].first) != on_x_res.end()) ans += on_x_res[a[i].first];
        on_x_res[a[i].first] += on_y[a[i].second]-1;
    }
    cout<<ans<<endl;
}

• Subtask 1: 100 / 100