Submission #1114072

#	Time	Username	Problem	Language	Result	Execution time	Memory
1114072		Dan4Life	The Kingdom of JOIOI (JOI17_joioi)	C++17	100 / 100	3374 ms	108636 KiB

joioi

#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) begin(a),end(a)
const int N = (int)2e3+10;
int n, m;
int dp[N][N], pref[N][N];
int a[N][N], b[N][N], c[N][N];
 
void Rotate(){
	for(int i = 0; i < n; i++)
		for(int j = 0; j < m; j++)
			c[i][j] = b[i][j];
	for(int i = 0; i < n; i++)
		for(int j = 0; j < m; j++)
			b[j][i] = c[i][m-j-1];
	swap(n,m);
}
 
bool calc(){
	for(int k : {0,1}){
		memset(dp,0,sizeof(dp));
		for(int i = 0; i < n; i++){
			for(int j = 0; j < m; j++){
				pref[i][j+1] = pref[i][j]+(!b[i][j] or b[i][j]==k);
			}
		}
		int bst=-1,bst2;
		for(int i = 0; i < n; i++){
			bst2=-1; int sum = 0, lst = 0;
			for(int j = 0; j < m; j++) if(b[i][j]==k) lst=j+1;
			for(int j = lst; j <= m; j++){
				if(pref[i][j]!=j) break;
				if(!i) dp[i][j]=(j!=m);
				else if(bst!=-1) dp[i][j]=(bst<=j);
				if(dp[i][j] and bst2==-1) bst2=j;
			}
			bst=bst2;
		}
		bool ok = 0;
		for(int i = 1; i <= m; i++) ok|=dp[n-1][i];
		if(ok) return 1;
	}
	return 0;
}
 
int mn = (int)1e9, mx = 0;
bool chk(int R){
	memset(b,0,sizeof(b));
	for(int i = 0; i < n; i++){
		for(int j = 0; j < m; j++){
			if(a[i][j]>mn+R) b[i][j]=2;
			if(a[i][j]<mx-R){
				if(b[i][j]==2) return 0;
				b[i][j] = 1;
			}
		}
	}
	bool ok = 0;
	for(int i = 0; i < 4; i++) 
		ok|=calc(), Rotate();
	return ok;
}
 
int main(){
	ios_base::sync_with_stdio(false); cin.tie(0);
	cin >> n >> m;
	for(int i = 0; i < n; i++)
		for(int j = 0; j < m; j++)
			cin >> a[i][j],mn=min(mn,a[i][j]),mx=max(mx,a[i][j]);
	int l = 0, r = mx-mn;
	while(l<r){
		int mid = (l+r)/2;
		if(chk(mid)) r=mid;
		else l=mid+1;
	}
	cout << l << "\n";
}

Compilation message (stderr)

joioi.cpp: In function 'bool calc()':
joioi.cpp:31:17: warning: unused variable 'sum' [-Wunused-variable]
   31 |    bst2=-1; int sum = 0, lst = 0;
      |                 ^~~

• Subtask 1: 15 / 15
• Subtask 2: 45 / 45
• Subtask 3: 40 / 40