Submission #547685

#	Time	Username	Problem	Language	Result	Execution time	Memory
547685		SmolBrain	Luxury burrow (IZhO13_burrow)	C++17	100 / 100	694 ms	25664 KiB

burrow

// Om Namah Shivaya
// GM in 114 days

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define endl '\n'
#define pb push_back
#define conts continue
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define ff first
#define ss second
#define ceil2(x,y) ((x+y-1) / (y))
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#ifndef ONLINE_JUDGE
#define debug(x) cout << #x <<" = "; print(x); cout << endl
#else
#define debug(x)
#endif

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

bool iseven(ll n) {if ((n & 1) == 0) return true; return false;}

void print(ll t) {cout << t;}
void print(int t) {cout << t;}
void print(string t) {cout << t;}
void print(char t) {cout << t;}
void print(double t) {cout << t;}
void print(ld t) {cout << t;}

template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(pair <T, V> p) {cout << "{"; print(p.ff); cout << ","; print(p.ss); cout << "}";}
template <class T> void print(vector <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(set <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(multiset <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T, class V> void print(map <T, V> v) {cout << "[ "; for (auto i : v) {print(i); cout << " ";} cout << "]";}
template<typename T> void amin(T &a, T b) { a = min(a, b); }
template<typename T> void amax(T &a, T b) { a = max(a, b); }

void usaco(string filename) {
    freopen((filename + ".in").c_str(), "r", stdin);
    freopen((filename + ".out").c_str(), "w", stdout);
}

const int MOD = 1e9 + 7;
const int maxn = 1e5 + 5;
const int inf1 = 1e9 + 5;
const ll inf2 = ll(1e18) + 5;

void solve(int test_case)
{

    /*

    thanks to "Anuj Bhaiya" for making this video: https://youtu.be/oaN9ibZKMpA

    approach:
    binary search on the answer
    the array a[][] is simplified to b[][], which is a binary matrix
    so the problem has been reduced to the following:
    find the max area subrectangle of 1s in a binary matrix
    this can be solved using the following approach: https://youtu.be/oaN9ibZKMpA

    */

    ll n, m, k; cin >> n >> m >> k;
    ll a[n][m], b[n][m];
    rep(i, n) rep(j, m) cin >> a[i][j];

    ll l = 1, r = 1e9;
    ll mncost = -1, mxarea = -1;

    while (l <= r) {
        ll mid = (l + r) / 2;

        rep(i, n) rep(j, m) b[i][j] = (a[i][j] >= mid);

        vector<ll> arr(m);
        ll currmx = 0;

        rep(i, n) {
            rep(j, m) {
                if (b[i][j]) {
                    arr[j]++;
                }
                else {
                    arr[j] = 0;
                }
            }

            vector<ll> nseleft(m, -1), nseright(m, m);
            stack<ll> st;

            rep(j, m) {
                while (!st.empty() and arr[j] < arr[st.top()]) {
                    nseright[st.top()] = j;
                    st.pop();
                }

                st.push(j);
            }

            while (!st.empty()) st.pop();

            rev(j, m - 1, 0) {
                while (!st.empty() and arr[j] < arr[st.top()]) {
                    nseleft[st.top()] = j;
                    st.pop();
                }

                st.push(j);
            }

            while (!st.empty()) st.pop();

            rep(j, m) {
                ll l = nseleft[j] + 1, r = nseright[j] - 1;
                ll len = r - l + 1;
                ll area = len * arr[j];
                amax(currmx, area);
            }
        }

        if (currmx >= k) {
            mncost = mid;
            mxarea = currmx;
            l = mid + 1;
        }
        else {
            r = mid - 1;
        }
    }

    cout << mncost << " " << mxarea << endl;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;
    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Compilation message (stderr)

burrow.cpp: In function 'void usaco(std::string)':
burrow.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen((filename + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
burrow.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen((filename + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 100 / 100