Submission #697262

#	Time	Username	Problem	Language	Result	Execution time	Memory
697262		allllekssssa	Bomb (IZhO17_bomb)	C++14	59 / 100	921 ms	76748 KiB

bomb

#include<bits/stdc++.h>
 
using namespace std;


#define pii pair<int ,int>
#define pb push_back

const int maxN = 2600;
int n, m;
int a[maxN][maxN];
int d[maxN][maxN];
int c[maxN][maxN];
string s;
int cnt[maxN];

int getDSum(int x1, int y1, int x2, int y2) {
	if (x2 > n || y2 > m) return 0;
	return d[x2][y2] + d[x1 - 1][y1 - 1] - d[x1 - 1][y2] - d[x2][y1 - 1];
}
 
int getCSum(int x1, int y1, int x2, int y2) {
	x1 = max(x1, 1);
	y1 = max(y1, 1);
	return c[x2][y2] + c[x1 - 1][y1 - 1] - c[x1 - 1][y2] - c[x2][y1 - 1];
}
 
bool check(int x, int y) {
 
	for (int i = 1; i<=n; i++) {
		for (int j = 1; j<=m; j++) {
			c[i][j] = 0;
		}
	}
   
   for (int i = 1; i<=n; i++) {
   	 for (int j = 1; j<=m; j++) {
   	 	if (getDSum(i, j, i + x - 1, j + y - 1) == x * y) c[i][j] = 1;
   	 }
   }
 
   for (int i = 1; i <= n; i++) {
		for (int j = 1; j<=m; j++) {
			c[i][j] += c[i - 1][j] + c[i][j - 1] - c[i - 1][j - 1];
		}
	}
 
   for (int i = 1; i<=n; i++) {
   	for (int j = 1; j <= m; j++) {
 		  if (a[i][j] && getCSum(i - x + 1, j - y + 1, i, j) == 0) return false;
   	  }
   }
 
   return true;
}

int heuristic1() {
    
	vector<pii> gornji;

	for (int i = 1; i<=n; i++) {
		for (int j = 1; j<=m; j++) {
			if (a[i - 1][j] == 0 && a[i][j - 1] == 0 && a[i][j] == 1) gornji.pb({i, j});
		}
	}

	// random_shuffle(gornji.begin(), gornji.end());
    
    for (int i = 1; i <=n; i++) {
    	cnt[i] = m;
    }

    for (int i = 0; i < min(2700, (int) gornji.size()); i++) {
       for (int len = 1; len <= n; len++) {
          
          int x = gornji[i].first;
          int y = gornji[i].second;

       	  int lo = -1;
       	  int ro = m + 1;
 
       	  while(lo < ro - 1) {
       	  	 int mid = lo + ro >> 1;
       	  	 if (getDSum(x, y, x + len - 1, y + mid - 1) == len * mid) lo = mid; else ro = mid;
       	  }

       	  cnt[len] = min(cnt[len], lo);
       }
    }


    int ans = 0;
    for (int i = 1; i<=n; i++) {
    	ans = max(ans, i * cnt[i]);
    }

    return ans;
}
 
int heuristic() {
  
   int minW = n;
   int minH = m;

	for (int i = 1; i<=n; i++) {
		int cur = 0;
		for (int j = 1; j<=m; j++) {
			if (a[i][j] == 1) cur++; else {
				if (cur > 0) {
					minH = min(minH, cur);
					cur = 0;
				}
			}
		}

	   if (cur > 0) minH = min(minH, cur);
	}

	for (int j = 1; j<=m; j++) {
		int cur = 0;
		for (int i = 1; i<=n; i++) {
			if (a[i][j] == 1) cur++; else {
				if (cur > 0) {
					minW = min(minW, cur);
					cur = 0;
				}
			}
		}

		if (cur > 0) minW = min(minW, cur);
	}
    
    int ans = minW * minH;
    if (!check(minW, minH)) return heuristic1();
	return ans;
}

int main() {
 
	cin >> n >> m;
 
	for (int i = 1; i <=n; i++) {
		cin >> s;
 
		for (int j = 0; j < m; j++) {
			a[i][j + 1] = s[j] - '0';
		}
	}
    
    for (int i = 1; i <= n; i++) {
		for (int j = 1; j<=m; j++) {
			d[i][j] = d[i - 1][j] + d[i][j - 1] + a[i][j] - d[i - 1][j - 1];
		}
	}

	if (n > 450 || m > 450) {
		cout << heuristic() << endl;
		return 0;
	}

   
    int ans = 0;
    
    int width = m;
	for (int i = 1; i <=n; i++) {
 
		while (width > 0 && !check(i, width)) width--;
 
		ans = max(ans, i * width);
	}
    
    cout << ans << endl;
}

Compilation message (stderr)

bomb.cpp: In function 'int heuristic1()':
bomb.cpp:83:26: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   83 |             int mid = lo + ro >> 1;
      |                       ~~~^~~~

• Subtask 1: 59 / 100