This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#define pb push_back
#define s second
#define f first
#define pb push_back
#define pii pair <int,int>
#define ll long long
// #define int ll
using namespace std;
const int N = 2e3 + 3;
int a[N][N],n,m,mn,mx,cnt[N];
bool vis[N][N],cur[N][N];
void clear(){
for (int i=1;i<=n;i++)
for(int j = 1; j <= m;j++)
vis[i][j]=0;
}
void go(int x,int y,int d){
if (x < 1 || y < 1 || x > n || y > m || vis[x][y]) return;
if (a[x][y] - mn > d) return;
vis[x][y] = 1;
go(x+1,y,d);
go(x-1,y,d);
go(x,y+1,d);
go(x,y-1,d);
}
int get(){
int mn1=-1,mx1=-1,mn2=-1,mx2=-1;
for (int i= 1; i <= n; i++){
for (int j= 1;j<=m;j++){
if(cur[i][j]){
if (mn1 == -1) {
mn1 = mx1 = a[i][j];
}else{
mn1 = min(mn1,a[i][j]);
mx1 = max(mx1,a[i][j]);
}
}else{
if (mn2 == -1) {
mn2 = mx2 = a[i][j];
}else{
mn2 = min(mn2,a[i][j]);
mx2 = max(mx2,a[i][j]);
}
}
}
}
return max(mx2-mn2,mx1-mn1);
}
bool go1(int d,bool dir){
for (int i = 1; i <= n; i++)
for (int j = 1; j <= n; j++)
cur[i][j] = 0;
int mnn = 2e9;
for (int i = 1; i <= n; i++){
mnn = min(mnn,cnt[i]);
if (!dir){
for (int j = m; j >= m - mnn + 1; j--){
cur[i][j] = 1;
}
}else{
for (int j = 1; j <= mnn; j++){
cur[i][j] = 1;
}
}
}
return (get() <= d);
}
bool go2(int d,bool dir){
for (int i = 1; i <= n; i++)
for (int j = 1; j <= n; j++)
cur[i][j] = 0;
int mnn = 2e9;
for (int i = n; i >= 1; i--){
mnn = min(mnn,cnt[i]);
if (!dir){
for (int j = m; j >= m - mnn + 1; j--){
cur[i][j] = 1;
}
}else{
for (int j = 1; j <= mnn; j++){
cur[i][j] = 1;
}
}
}
return (get() <= d);
}
signed main() {
ios_base::sync_with_stdio(0),cin.tie(NULL),cout.tie(NULL);
cin>>n>>m;
mn = 2e9;
int X = 0,Y=0;
for (int i = 1; i <= n; i++){
for (int j = 1; j <= m; j++){
cin >> a[i][j];
if (a[i][j] < mn){
X=i,Y=j;
mn=a[i][j];
}
mx=max(mx,a[i][j]);
}
}
int l = 0,r = mx - mn,ans=mx-mn;
while (l <= r){
clear();
int mid=(l+r)/2;
go(X,Y,mid);
for (int i = 1; i <= n; i++){
cnt[i] = m;
for (int j = m; j >= 1; j--){
if (!vis[i][j]){
cnt[i] = m - j;
break;
}
}
}
if (go1(mid,0) || go2(mid,0)){
ans=mid;
r=mid-1;
continue;
}
for (int i = 1; i <= n; i++){
cnt[i] = m;
for (int j = 1; j <= m; j++){
if (!vis[i][j]){
cnt[i] = j - 1;
break;
}
}
}
if (go1(mid,1) || go2(mid,1)){
ans=mid;
r=mid-1;
continue;
}
l = mid + 1;
}
cout<<ans<<endl;
}
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