Language: C++

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <stack>
#include <map>
#include <queue>
#include <cmath>
#include <iomanip>
#include <set>
#include <functional>
#include <list>

#define MOD (1000000000 + 7)

using namespace std;

typedef long long ll;
const int MAX = 3000000;

long long fac[MAX], finv[MAX], inv[MAX];

long long modinv(long long a, long long m) {
    long long b = m, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m;
    if (u < 0) u += m;
    return u;
}

ll modpow(ll a, ll n, ll mod) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}

ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b;}
// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

// 二項係数計算
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

map<ll,ll> prime;//素因数分解でそれぞれの素数がいくつ出てきたかを保存するmap

//O(√n)
//整列済み(mapはkeyで自動で整列される)
void prime_factorize(ll n){
    if(n<=1) return;
    ll l=sqrt(n);
   for(ll i=2;i<=(ll)(l);i++) { //
        if(n%i==0){
            prime_factorize(i);prime_factorize(ll(n/i));return;
        }
    }
    //mapでは存在しないkeyの場合も自動で構築される
    prime[n]++;return;
} 

// 約数列挙？
vector<ll> divisor;
void list_divisor(ll n) {
    divisor.clear();
    for(int i = 1; i*i <= n; i++) {
        if(n % i == 0) {
            divisor.push_back(i);
            if(i*i != n) divisor.push_back(n/i);
        }
    }
    sort(divisor.begin(), divisor.end());
}

vector<bool> Eratosthenes(ll N) {
    vector<bool> primes(N, true);
    vector<ll> ret;
    primes[0] = false;
    primes[1] = false;
    for (ll i=2; pow(i,2)<=N; i++) {
        if (primes[i]) {
            for(int j=2; i*j<=N; j++) primes[i*j] = false;
            ret.push_back(primes[i]);
        }
    }
    return primes;//ret;
}

template <typename T> bool next_combination(const T first, const T last, int k) {
    // ** Sample **
    // vector<int> v{1, 2, 3, 4, 5, 6, 7};
    // do {
    //     for (int i = 0; i < k; i++) {
    //         cout << v[i] << " ";
    //     }
    //     cout << "| ";
    //     for (int i = k; i < v.size(); i++) {
    //         cout << v[i] << " ";
    //     }
    //     cout << endl;
    // } while(next_combination(v.begin(), v.end(), k));

    const T subset = first + k;
    // empty container | k = 0 | k == n 
    if (first == last || first == subset || last == subset) {
        return false;
    }
    T src = subset;
    while (first != src) {
        src--;
        if (*src < *(last - 1)) {
            T dest = subset;
            while (*src >= *dest) {
                dest++;
            }
            iter_swap(src, dest);
            rotate(src + 1, dest + 1, last);
            rotate(subset, subset + (last - dest) - 1, last);
            return true;
        }
    }
    // restore
    rotate(first, subset, last);
    return false;
}

// union by size + path having
class UnionFind {
public:
    vector <ll> par; // 各元の親を表す配列
    vector <ll> siz; // 素集合のサイズを表す配列(1 で初期化)

    // Constructor
    UnionFind(ll sz_): par(sz_), siz(sz_, 1LL) {
        for (ll i = 0; i < sz_; ++i) par[i] = i; // 初期では親は自分自身
    }
    void init(ll sz_) {
        par.resize(sz_);
        siz.assign(sz_, 1LL);  // resize だとなぜか初期化されなかった
        for (ll i = 0; i < sz_; ++i) par[i] = i; // 初期では親は自分自身
    }

    // Member Function
    // Find
    ll root(ll x) { // 根の検索
        while (par[x] != x) {
            x = par[x] = par[par[x]]; // x の親の親を x の親とする
        }
        return x;
    }

    // Union(Unite, Merge)
    bool merge(ll x, ll y) {
        x = root(x);
        y = root(y);
        if (x == y) return false;
        // merge technique（データ構造をマージするテク．小を大にくっつける）
        if (siz[x] < siz[y]) swap(x, y);
        siz[x] += siz[y];
        par[y] = x;
        return true;
    }

    bool issame(ll x, ll y) { // 連結判定
        return root(x) == root(y);
    }

    ll size(ll x) { // 素集合のサイズ
        return siz[root(x)];
    }
};
// auto compare = [](pair<ll, ll> a, pair<ll, ll> b) {
//     ll a_mp = get<1>(a);
//     ll b_mp = get<1>(b);
//     return a_mp < b_mp;
//     // if (a_mp != b_mp) return a_mp > b_mp;
//     // else return get<0>(a) > get<0>(b);
// };

ll H, W;
bool push_queue(vector<vector<char>> &m, queue<tuple<ll,ll,ll>> &q, vector<vector<ll>> &seen, ll h, ll w, ll magic) {
    if(h >= H || w >= W || h < 0 || w < 0) return false;
    if(m[h][w] != '.') return false;
    if(seen[h][w] <= magic) return false;

    q.push(make_tuple(h, w, magic));
    seen[h][w] = magic;
    return true;
}

bool check(vector<ll> &h, vector<ll> &w, ll h_, ll w_) {
    for(ll i = 0; i < M; i++) {
        if(h[i] == h_ && w[i] == w_) return true;
    }
    return false;
}

int main() {
    //E
    ll H, W, M;
    cin >> H >> W >> M;

    vector<ll> h(M, 0), w(M, 0);
    vector<ll> hcount(M, 0), wcount(M, 0);
    ll hmax = 0, wmax = 0;


    for(ll i = 0; i < M; i++) {
        ll hi, wi;
        cin >> hi >> wi;
        h[i] = hi-1;
        w[i] = wi-1;


        hcount[h[i]] ++;
        wcount[w[i]] ++;
        
        hmax = max(hmax, hcount[h[i]]);
        wmax = max(wmax, wcount[w[i]]);
    }

    map<ll, vector<ll>> wm;
    map<ll, vector<ll>> hm;
    for(ll i = 0; i < W; i++) { 
        wm[wcount[i]].push_back(i);
    }
    for(ll i = 0; i < H; i++) { 
        hm[hcount[i]].push_back(i);
    }

    for(ll i = 0; i < hm[hmax].size(); i++) {
        for(ll j = 0; j < wm[wmax].size(); j++) {
            // cout << hm[hmax][i] << "," << wm[wmax][j] << endl;
            if(check(h, w, hm[hmax][i], wm[wmax][j])) {
                cout << hmax + wmax << endl;
                return 0;
            }
        }
    }
    cout << hmax + wmax - 1 << endl;
    //D
    // cin >> H >> W;

    // ll Ch, Cw;
    // cin >> Ch >> Cw;
    // Ch -= 1;
    // Cw -= 1;

    // ll Dh, Dw;
    // cin >> Dh >> Dw;
    // Dh -= 1;
    // Dw -= 1;

    // vector<vector<char>> map(H, vector<char>(W, '.'));
    // for(ll i = 0; i < H; i++) {
    //     for(ll j = 0; j < W; j++) {
    //         cin >> map[i][j];
    //     }
    // }

    // queue<tuple<ll, ll, ll>> q, q2;
    // q.push(make_tuple(Ch, Cw, 0));
    // vector<vector<ll>> seen(H, vector<ll>(W, 9999999));
    // while(q.size() > 0 || q2.size() > 0) {
    //     tuple<ll, ll,ll> tup;
    //     if(q.size() == 0) {
    //         tup = q2.front(); q2.pop();
    //     } else {
    //         tup = q.front(); q.pop();
    //     }
    //     ll h = get<0>(tup);
    //     ll w = get<1>(tup);
    //     ll magic = get<2>(tup);

    //     // cout << h << "," << w << ":" << magic << endl;

    //     for(ll i = -2; i <= 2; i++) {
    //         for(ll j = -2 ; j <= 2; j++) {
    //             if( i== 0 && j == 0) continue;
    //             if( (i == 0 && abs(j) == 1) || (j == 0 && abs(i) == 1))
    //                 push_queue(map, q, seen, h + i, w + j, magic);
    //             else
    //                 push_queue(map, q2, seen, h + i, w + j, magic+1);
    //         }
    //     }
    // }

    // if(seen[Dh][Dw] == 9999999) cout << -1 << endl;
    // else cout << seen[Dh][Dw] << endl;


    return 0;
}


Compiler output:
a.cc: In function 'bool check(std::vector<long long int>&, std::vector<long long int>&, ll, ll)':
a.cc:212:23: error: 'M' was not declared in this scope
  212 |     for(ll i = 0; i < M; i++) {
      |                       ^