Submission #165639

#	Time	Username	Problem	Language	Result	Execution time	Memory
165639		qkxwsm	Bomb (IZhO17_bomb)	C++14	100 / 100	410 ms	56568 KiB

bomb

#include <bits/stdc++.h>

using namespace std;

template<class T, class U>
void ckmin(T &a, U b)
{
	if (a > b) a = b;
}
template<class T, class U>
void ckmax(T &a, U b)
{
	if (a < b) a = b;
}

#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)
#define SZ(x) ((int) ((x).size()))
#define ALL(x) (x).begin(), (x).end()
#define MAXN 2513
#define INF 1000000007

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpi;
typedef vector<pll> vpl;

int N, M;
bitset<MAXN> grid[MAXN];
int up[MAXN][MAXN], dn[MAXN][MAXN];
int dp[MAXN];
int ans;
int width = INF;

int32_t main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	cout << fixed << setprecision(12);
	cerr << fixed << setprecision(4);
	cin >> N >> M;
	FOR(i, 0, N)
	{
		string temps; cin >> temps;
		FOR(j, 0, M)
		{
			grid[i][j] = (temps[j] == '1');
		}
	}
	//length of shortest vertical strip.
	FOR(i, 0, M + 1)
	{
		dp[i] = INF;
	}
	// cerr << dp[2] << endl;
	FOR(i, 0, M)
	{
		int sum = 0;
		FOR(j, 0, N)
		{
			if (grid[j][i]) sum++;
			else
			{
				if (sum) ckmin(dp[1], sum);
				sum = 0;
			}
		}
		if (sum) ckmin(dp[1], sum);
	}
	FOR(i, 0, N)
	{
		int sum = 0;
		FOR(j, 0, M)
		{
			if (grid[i][j]) sum++;
			else
			{
				if (sum) ckmin(width, sum);
				sum = 0;
			}
		}
		if (sum) ckmin(width, sum);
	}
	if (width >= INF)
	{
		cout << N * M << '\n';
		return 0;
	}
	// cerr << dp[1] << endl;
	FOR(j, 0, M)
	{
		FOR(i, 0, N)
		{
			if (!grid[i][j]) up[i][j] = i + 1;
			else up[i][j] = (i == 0 ? 0 : up[i - 1][j]);
		}
		FORD(i, N, 0)
		{
			if (!grid[i][j]) dn[i][j] = i - 1;
			else dn[i][j] = (i == N - 1 ? N - 1 : dn[i + 1][j]);
		}
	}
	// FOR(i, 0, N)
	// {
	// 	FOR(j, 0, M)
	// 	{
	// 		cerr << up[i][j] << ' ';
	// 	}
	// 	cerr << endl;
	// }
	// FOR(i, 0, N)
	// {
	// 	FOR(j, 0, M)
	// 	{
	// 		cerr << dn[i][j] << ' ';
	// 	}
	// 	cerr << endl;
	// }
	FOR(i, 0, N)
	{
		int sum = 0; pii bound = {0, N - 1};
		FOR(j, 0, M)
		{
			if (grid[i][j])
			{
				sum++;
				ckmin(bound.se, dn[i][j]);
				ckmax(bound.fi, up[i][j]);
			}
			else
			{
				sum = 0;
				bound = {0, N - 1};
			}
			if (sum > 1) ckmin(dp[sum], bound.se - bound.fi + 1);
			// cerr << sum << ',' << bound.se << ' ' << bound.fi << ' ' << bound.se - bound.fi + 1 << ' ';
		}
		// cerr << endl;
	}
	FOR(i, 0, N)
	{
		int sum = 0; pii bound = {0, N - 1};
		FORD(j, M, 0)
		{
			if (grid[i][j])
			{
				sum++;
				ckmin(bound.se, dn[i][j]);
				ckmax(bound.fi, up[i][j]);
			}
			else
			{
				sum = 0;
				bound = {0, N - 1};
			}
			if (sum > 1) ckmin(dp[sum], bound.se - bound.fi + 1);
			// cerr << sum << ',' << bound.se - bound.fi + 1 << ' ';
		}
		// cerr << endl;
	}
	FOR(i, 1, width + 1)
	{
		ckmin(dp[i], dp[1]);
		ckmax(ans, dp[i] * i);
		// cerr << dp[i] << endl;
	}
	cout << ans << '\n';
	return 0;
}

• Subtask 1: 100 / 100