test/DPL3B.test.cpp

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• category: test
• View this file on GitHub
  • Last commit date: 2020-04-08 18:07:26+09:00
• see: https://onlinejudge.u-aizu.ac.jp/courses/library/7/DPL/3/DPL_3_B

Depends on

• DP/largest_rectangle.cpp
• memo/macro.hpp

Code

#define PROBLEM "https://onlinejudge.u-aizu.ac.jp/courses/library/7/DPL/3/DPL_3_B"
#include "../memo/macro.hpp"
#include "../DP/largest_rectangle.cpp"

signed main(void) {
    ll h, w;
    cin >> h >> w;
    vector<vector<ll>> c(h, vector<ll>(w));
    REP(i, h) REP(j, w) cin >> c[i][j];

    cout << largeest_rectangle(c) << endl;

    return 0;
}

#line 1 "test/DPL3B.test.cpp"
#define PROBLEM "https://onlinejudge.u-aizu.ac.jp/courses/library/7/DPL/3/DPL_3_B"
#line 1 "memo/macro.hpp"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using PII = pair<ll, ll>;
#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
template<typename T> void chmin(T &a, const T &b) { a = min(a, b); }
template<typename T> void chmax(T &a, const T &b) { a = max(a, b); }
struct FastIO {FastIO() { cin.tie(0); ios::sync_with_stdio(0); }}fastiofastio;
const ll INF = 1LL<<60;
#line 1 "DP/largest_rectangle.cpp"
// BEGIN CUT
// i番目の高さがh[i]のヒストグラム中で最大の長方形の面積
ll largest_rectangle_histogram(vector<ll> h) {
    const ll n = h.size();

    // iを固定して高さがh[i]となる長方形を考えるとl,rは一意に定まる
    // l[i], r[i] をstackを使って求める

    // l[i] = (j<=iかつh[j-1]<h[i]となる最大のj)
    vector<ll> l(n);
    stack<ll> st1;
    REP(i, n) {
        while(st1.size() && h[st1.top()] >= h[i]) st1.pop();
        l[i] = st1.empty() ? 0 : (st1.top()+1);
        st1.push(i);
    }
    // r[i] = (j>iかつh[j]<h[i]となる最小のj)
    vector<ll> r(n);
    stack<ll> st2;
    for(ll i=n-1; i>=0; --i) {
        while(st2.size() && h[st2.top()] >= h[i]) st2.pop();
        r[i] = st2.empty() ? n : st2.top();
        st2.push(i);
    }
    ll ret = 0;
    REP(i, n) ret = max(ret, h[i]*(r[i]-l[i]));
    return ret;
}

// c[i][j] = 0 のマスだけを使って構成できる最大の長方形の面積を返す
ll largeest_rectangle(vector<vector<ll>> c) {
    const int h = c.size(), w = c[0].size();
    vector<vector<ll>> con(h, vector<ll>(w));

    REP(i, w) {
        int cnt = 1;
        REP(j, h) {
            if(!c[j][i]) {
                con[j][i] = cnt;
                cnt++;
            } else {
                con[j][i] = 0;
                cnt = 1;
            }
        }
    }

    ll ret = 0;
    REP(i, h) chmax(ret, largest_rectangle_histogram(con[i]));
    return ret;
}
// END CUT
#line 4 "test/DPL3B.test.cpp"

signed main(void) {
    ll h, w;
    cin >> h >> w;
    vector<vector<ll>> c(h, vector<ll>(w));
    REP(i, h) REP(j, w) cin >> c[i][j];

    cout << largeest_rectangle(c) << endl;

    return 0;
}

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