//clever
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
random_device(rd);
mt19937 rng(rd());
const long long FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
struct custom_hash
{
template<class T>
unsigned long long operator()(T v) const
{
unsigned long long x = v;
x += FIXED_RANDOM;
// x += 11400714819323198485ull;
// x = (x ^ (x >> 30)) * 13787848793156543929ull;
x = (x ^ (x >> 27)) * 10723151780598845931ull;
return x ^ (x >> 31);
}
};
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T, class U> using hash_table = gp_hash_table<T, U, custom_hash>;
template<class T>
T randomize(T mod)
{
return (uniform_int_distribution<T>(0, mod - 1))(rng);
}
template<class T>
void readi(T &x)
{
x = 0;
bool negative = false;
char c = ' ';
while (c < '-')
{
c = getchar();
}
if (c == '-')
{
negative = true;
c = getchar();
}
while (c >= '0')
{
x = x * 10 + (c - '0');
c = getchar();
}
if (negative)
{
x = -x;
}
}
template<class T>
void printi(T output)
{
if (output == 0)
{
putchar('0');
return;
}
if (output < 0)
{
putchar('-');
output = -output;
}
int buf[20], n = 0;
while(output)
{
buf[n] = ((output % 10));
output /= 10;
n++;
}
for (n--; n >= 0; n--)
{
putchar(buf[n] + '0');
}
return;
}
template<class T>
void ckmin(T &a, T b)
{
a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
a = max(a, b);
}
long long expo(long long a, long long e, long long mod)
{
return ((e == 0) ? 1 : ((expo(a * a % mod, e >> 1, mod)) * ((e & 1) ? a : 1) % mod));
}
template<class T, class U>
void nmod(T &x, U mod)
{
if (x >= mod) x -= mod;
}
template<class T>
T gcd(T a, T b)
{
return (b ? gcd(b, a % b) : a);
}
#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define DBG(x) cerr << #x << " = " << (x) << endl
#define SZ(x) ((int) ((x).size()))
#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 ALL(x) (x).begin(), (x).end()
const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-9;
#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 2013
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<ld> vd;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
typedef vector<pdd> vpd;
int N, M;
int grid[MAXN][MAXN];
int big, small = INF;
pii bigpos, smallpos;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, -1, 0, 1};
pii range[MAXN];
struct dsu
{
pii dsu[MAXN][MAXN];
pii get(pii p)
{
if (dsu[p.fi][p.se] == p) return p;
dsu[p.fi][p.se] = get(dsu[p.fi][p.se]);
return dsu[p.fi][p.se];
}
void merge(pii a, pii b)
{
a = get(a);
b = get(b);
dsu[a.fi][a.se] = b;
}
void init()
{
FOR(i, 0, N)
{
FOR(j, 0, M)
{
dsu[i][j] = {i, j};
}
}
}
};
dsu S, B;
bool valid(int x, int y)
{
return (0 <= x && x < N && 0 <= y && y < M);
}
bool ok()
{
//these are the first guys that do not approve!
FOR(i, 0, N)
{
if (range[i].fi > range[i].se) return false;
}
bool flag = true; int pos = 0;
FOR(i, 0, N)
{
//the guy can be in the range (range[i].fi, range[i].se)
if (range[i].se < pos)
{
flag = false; break;
}
ckmax(pos, range[i].fi);
}
if (flag) return true;
flag = true; pos = M - 1;
FOR(i, 0, N)
{
if (range[i].fi > pos)
{
flag = false; break;
}
ckmin(pos, range[i].se);
}
if (flag) return true;
return false;
}
bool check(int x)
{
S.init();
B.init();
FOR(i, 0, N)
{
FOR(j, 0, M)
{
if (grid[i][j] > small + x) continue;
FOR(k, 0, 2)
{
pii p = {i + dx[k], j + dy[k]};
if (valid(p.fi, p.se) && grid[p.fi][p.se] <= small + x)
{
S.merge({i, j}, p);
}
}
}
}
FOR(i, 0, N)
{
FOR(j, 0, M)
{
if (grid[i][j] < big - x) continue;
FOR(k, 0, 2)
{
pii p = {i + dx[k], j + dy[k]};
if (valid(p.fi, p.se) && grid[p.fi][p.se] >= big - x)
{
B.merge({i, j}, p);
}
}
}
}
//try to have SMALL be an increasing/decreasing sequence!
FOR(i, 0, N)
{
for (range[i].se = 0; range[i].se < M; range[i].se++)
{
if (S.get({i, range[i].se}) != S.get(smallpos)) break;
}
for (range[i].fi = M - 1; range[i].fi >= 0; range[i].fi--)
{
if (B.get({i, range[i].fi}) != B.get(bigpos)) break;
}
}
if (ok())
{
return true;
}
//try to have BIG be an increasing/decreasing sequence
FOR(i, 0, N)
{
for (range[i].se = 0; range[i].se < M; range[i].se++)
{
if (B.get({i, range[i].se}) != B.get(bigpos)) break;
}
for (range[i].fi = M - 1; range[i].fi >= 0; range[i].fi--)
{
if (S.get({i, range[i].fi}) != S.get(smallpos)) break;
}
}
if (ok())
{
return true;
}
return false;
}
int32_t main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
// cout << fixed << setprecision(10);
// cerr << fixed << setprecision(10);
// if (fopen("file.in", "r"))
// {
// freopen ("file.in", "r", stdin);
// freopen ("file.out", "w", stdout);
// }
cin >> N >> M;
FOR(i, 0, N)
{
FOR(j, 0, M)
{
cin >> grid[i][j];
if (grid[i][j] > big)
{
big = grid[i][j];
bigpos = {i, j};
}
if (grid[i][j] < small)
{
small = grid[i][j];
smallpos = {i, j};
}
}
}
// cerr << smallpos.fi << ' ' << smallpos.se << ' ' << bigpos.fi << ' ' << bigpos.se << endl;
int lo = 0, hi = big - small;
while(hi > lo)
{
int mid = (hi + lo) >> 1;
if (check(mid)) hi = mid;
else lo = mid + 1;
}
cout << lo << '\n';
// cerr << "time elapsed = " << (clock() / (CLOCKS_PER_SEC / 1000)) << " ms" << endl;
return 0;
}
/* READ READ READ
* int overflow, maxn too small, special cases (n=1?, two distinct?), cin.tie() interactive
* reread the problem, try small cases
* note down possible sources of error as you go
* do smth instead of nothing
*/
Compilation message
g++-7: internal compiler error: Killed (program cc1plus)
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions.
