C - Watchmen CodeForces - 651C （使用map例题）

#include<iostream>#include<map> using namespace std;map<int,int> x;map<int,int> y;map<pair<int,int>,int> xy;int main(){    int n;    cin>>n;    for(int i=0;i<n;++i)    {        int xx,yy;        scanf("%d%d",&xx,&yy);        ++x[xx];        ++y[yy];        ++xy[make_pair(xx,yy)];    }    long long ans=0;    for(auto i : x) ans+=(long long)i.second*((long long)i.second-1)/2;    for(auto i : y) ans+=(long long)i.second*((long long)i.second-1)/2;    for(auto i : xy) ans-=(long long)i.second*((long long)i.second-1)/2;    printf("%lld",ans);  }