1147 - Maximum Building I.cpp

/*
Problem Name: Maximum Building I
Problem Link: https://cses.fi/problemset/task/1147
Author: Sachin Srivastava (mrsac7)
*/
#include<bits/stdc++.h>
using namespace std;

#define int long long
#define endl '\n'

int a[1005];
signed main(){
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    #ifdef LOCAL
    freopen("input.txt", "r" , stdin);
    freopen("output.txt", "w", stdout);
    #endif
    
    int n,m; cin>>n>>m;
    int mx = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            char x; cin>>x;
            if (x == '.') a[j]++;
            else a[j] = 0;
        }
        stack<int> st;
        for (int j = 0; j <= m; j++) { //pseudo element at end
            while(!st.empty() && a[st.top()] > a[j]) {
                int s = st.top(); st.pop();
                int area = a[s]*(st.empty() ? j : j-st.top()-1);
                mx = max(mx, area);
            }
            if (j < m) st.push(j);
        }
    }
    cout<<mx;
}