ABC 023-C 収集王

ABC023C.cpp

#include<iostream>
#include<vector>
#include<stdio.h>
#define rep(i, n) for(int i=0; i<(n); i++)
#define pb push_back
 
using namespace std;
 
int main(){
 
    int R, C, K, N;
    cin>> R>> C>> K>> N;
    vector<int> r, c;
    rep(i, N){
        int a, b;
        scanf("%d %d", &a, &b);
        a--; b--;
        r.pb(a); c.pb(b);
    }
 
    vector<int> row(R, 0), col(C, 0);
    rep(i, N){
        row[r[i]]++;
        col[c[i]]++;
    }
 
    vector<pair<int, int> > cd(N+1, make_pair(0, 0));// <raw, col>
    rep(i, R) cd[row[i]].first++;
    rep(j, C) cd[col[j]].second++;
 
    long long ans=0;
    for(int i=0; i<=K; i++){
        ans+=cd[i].first*cd[K-i].second;
    }
 
    rep(i, N){
        if(row[r[i]]+col[c[i]]==K+1) ans++;
        if(row[r[i]]+col[c[i]]==K) ans--;
    }
 
    cout<< ans<< endl;
 
    return 0;
}