Submission #391746

#	Time	Username	Problem	Language	Result	Execution time	Memory
391746		patrikpavic2	Bomb (IZhO17_bomb)	C++17	100 / 100	744 ms	96468 KiB

bomb

#include <cstdio>
#include <algorithm>
#include <vector>
#include <cstring>
 
#define PB push_back
 
using namespace std;
 
const int N = 2505;
 
int n, m;
char s[N][N];
int A[N][N], B[N][N];
 
int par[N], L[N], R[N], un[N], nula[N];
int S[N];
 
int pr(int x){
	if(x == par[x]) return x;
	return par[x] = pr(par[x]);
}
 
void mrg(int x, int y){
	if(x < 0 || y >= m || !un[x] || !un[y]) return;
//	printf("mrg %d %d\n", x, y);
	x = pr(x), y = pr(y);
	if(x == y) return;
	if(nula[x]) S[R[x] - L[x] + 1]--; 
	if(nula[y]) S[R[y] - L[y] + 1]--;
	if(R[x] - L[x] > R[y] - L[y]){
		par[y] = x; R[x] = R[y];
		nula[x] |= nula[y];
		if(nula[x])
			S[R[x] - L[x] + 1]++;
	}
	else{
		par[x] = y; L[y] = L[x];
		nula[y] |= nula[x];
		if(nula[y])
			S[R[y] - L[y] + 1]++;
	}
}
 
vector < int > kon[N];
int ans[N];
 
void odradi_redak(int rd){
	for(int i = 0;i <= m;i++) S[i] = 0;
	for(int i = 0;i <= n;i++) kon[i].clear();
	for(int i = 0;i < m;i++){
		un[i] = 0; 
		if(s[rd][i] == '0') continue;
		par[i] = i; nula[i] = (B[rd][i] == 1);
		L[i] = i, R[i] = i;
		kon[A[rd][i]].PB(i);
		if(nula[i]) S[0]++;
	}
	if(!S[0]) return;
	int cur = 0;
	for(int i = n;i >= 1;i--){
		for(int x : kon[i]){
			if(nula[x])
				S[0]--, S[1]++;
		//	printf("x = %d nula = %d\n", x, nula[x]);
			un[x] = 1;
			mrg(x - 1, x);
			mrg(x, x + 1);
		}
		while(!S[cur]) cur++;
		//printf("rd = %d i = %d cur = %d\n", rd, i, cur);
		ans[i] = min(ans[i], cur);
	}
}
 
int main(){
	//freopen("bomb.in", "r", stdin);
	//freopen("bomb.out", "w", stdout);
	scanf("%d%d", &n, &m);
	int fin = 0;
	for(int i = 0;i < n;i++)
		for(int j = 0;j < m;j++)
			scanf(" %c", &s[i][j]);
	for(int i = 1;i <= n;i++) ans[i] = m;
	for(int bla = 0;bla < 2;bla++){
		memset(A, 0, sizeof(A));
		memset(B, 0, sizeof(B));
		for(int i = 0;i < n;i++)
			for(int j = 0;j < m;j++)
				A[i][j] = (1 + (i ? A[i - 1][j] : 0)) * (s[i][j] - '0');
		for(int i = n - 1;i >= 0;i--)
			for(int j = 0;j < m;j++)
				B[i][j] = (1 + B[i + 1][j]) * (s[i][j] - '0');
		int min_j = n, min_i = m;
		for(int i = 0;i < n;i++)
			for(int j = 0;j < m;j++)
				if(s[i][j] == '1') min_j = min(min_j, A[i][j] + B[i][j] - 1);
		for(int i = 0;i < n;i++){
			for(int j = 0;j < m;){
				if(s[i][j] == '0'){
					j++; continue;
				}
				int jj = j;
				while(j < m && s[i][j] == '1') j++;
				min_i = min(min_i, j - jj);
			}
		}
		for(int i = 1;i <= min_j;i++) ans[i] = min(ans[i], min_i);
		for(int i = min_j + 1;i <= n;i++) ans[i] = 0; 
		for(int i = 0;i < n;i++) odradi_redak(i);
		for(int i = 0;n - i - 1 > i;i++){
			for(int j = 0;j < m;j++)
				swap(s[i][j], s[n - i - 1][j]);
		}
	}
	for(int i = 1;i <= n;i++){
		fin = max(fin, ans[i] * i);
	}
	printf("%d\n", fin);
	return 0;
}
 
/*
5 6
000000
111110
111110
111110
001000
 
*/

Compilation message (stderr)

bomb.cpp: In function 'int main()':
bomb.cpp:79:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   79 |  scanf("%d%d", &n, &m);
      |  ~~~~~^~~~~~~~~~~~~~~~
bomb.cpp:83:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   83 |    scanf(" %c", &s[i][j]);
      |    ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 100 / 100