Submission #770498

#	Time	Username	Problem	Language	Result	Execution time	Memory
770498		GrindMachine	The Kingdom of JOIOI (JOI17_joioi)	C++17	100 / 100	707 ms	196448 KiB

joioi

// Om Namah Shivaya
 
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
 
using namespace std;
using namespace __gnu_pbds;
 
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
 
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
 
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)
 
template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}
 
template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}
 
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
 
/*
 
refs:
https://codeforces.com/blog/entry/50413

(for 60 points):
stress tested to identify the bug: https://oj.uz/submission/767335
didnt set the bounds for the binary search properly (wrote n instead of m)

*/

const int MOD = 1e9 + 7;
const int N = 2e3 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
 
ll n,m;
ll a[N][N], pmn[N][N], pmx[N][N], smn[N][N], smx[N][N];
 
void solve(int test_case)
{
    cin >> n >> m;
    rep1(i,n) rep1(j,m) cin >> a[i][j];
 
    memset(pmn,0x10,sizeof pmn);
    memset(smn,0x10,sizeof smn);
    memset(pmx,-0x10,sizeof pmx);
    memset(smx,-0x10,sizeof smx);
 
    rep1(i,n){
        rep1(j,m){
            pmn[i][j] = min(pmn[i][j-1], a[i][j]);
            pmx[i][j] = max(pmx[i][j-1], a[i][j]);
        }
        rev(j,m,1){
            smn[i][j] = min(smn[i][j+1], a[i][j]);
            smx[i][j] = max(smx[i][j+1], a[i][j]);
        }
    }

    ll mn = inf2, mx = -inf2;
    rep1(i,n){
        rep1(j,m){
            amin(mn,a[i][j]);
            amax(mx,a[i][j]);
        }
    }

    auto ok = [&](ll k){
        // min territory, decreasing
        {
            ll prev_len = inf2;
            bool flag = true;

            rep1(i,n){
                ll len = 0;
                rep1(j,m){
                    if(a[i][j] <= mn+k){
                        len++;
                    }
                    else{
                        break;
                    }
                }

                amin(len,prev_len);
                prev_len = len;

                for(int j = len+1; j <= m; ++j){
                    if(a[i][j] < mx-k){
                        flag = false;
                    }
                }
            }

            if(flag) return true;
        }

        // min territory, decreasing
        {
            ll prev_len = inf2;
            bool flag = true;

            rev(i,n,1){
                ll len = 0;
                rep1(j,m){
                    if(a[i][j] <= mn+k){
                        len++;
                    }
                    else{
                        break;
                    }
                }

                amin(len,prev_len);
                prev_len = len;

                for(int j = len+1; j <= m; ++j){
                    if(a[i][j] < mx-k){
                        flag = false;
                    }
                }
            }

            if(flag) return true;
        }

        // max territory, decreasing
        {
            ll prev_len = inf2;
            bool flag = true;

            rep1(i,n){
                ll len = 0;
                rep1(j,m){
                    if(a[i][j] >= mx-k){
                        len++;
                    }
                    else{
                        break;
                    }
                }

                amin(len,prev_len);
                prev_len = len;

                for(int j = len+1; j <= m; ++j){
                    if(a[i][j] > mn+k){
                        flag = false;
                    }
                }
            }

            if(flag) return true;
        }

        // max territory, increasing
        {
            ll prev_len = inf2;
            bool flag = true;

            rev(i,n,1){
                ll len = 0;
                rep1(j,m){
                    if(a[i][j] >= mx-k){
                        len++;
                    }
                    else{
                        break;
                    }
                }

                amin(len,prev_len);
                prev_len = len;

                for(int j = len+1; j <= m; ++j){
                    if(a[i][j] > mn+k){
                        flag = false;
                    }
                }
            }

            if(flag) return true;
        }
        return false;
    };

    ll l = 0, r = inf1;
    ll ans = -1;

    while(l <= r){
        ll mid = (l+r) >> 1;
        if(ok(mid)){
            ans = mid;
            r = mid-1;
        }
        else{
            l = mid+1;
        }
    }    

    cout << ans << endl;
}
 
int main()
{
    fastio;
 
    int t = 1;
    // cin >> t;
 
    rep1(i, t) {
        solve(i);
    }
 
    return 0;
}

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