Submission #1286794

#	Time	Username	Problem	Language	Result	Execution time	Memory
1286794		samarthkulkarni	Mecho (IOI09_mecho)	C++20	4 / 100	557 ms	131072 KiB

mecho

#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;

#pragma GCC target ("avx2")
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC optimize("fast-math")

#define ll int
#define ld long double
#define vi vector<ll>
#define endl "\n"
#define pr pair<ll, ll>
#define ff first 
#define ss second
#define all(x) x.begin(), x.end()
const int mod = 1e9+7;
void _p(ll a){cout<<a<<endl;}
void _p(string a){cout<<a<<endl;}
void _p(ld a) {cout<<a<<endl;}
template <class T>
void _p(vector<T> a){for(T val:a)cout<<val<<" ";cout<<endl;}
#define debug(x) cout<<#x<<" -> ";_p(x)

typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update > ordered_set;

vector<pr> move8 = {{1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}, {-1, -1}, {0, -1}, {1, -1}};
vector<pr> move4 = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
vector<pr> move2 = {{0, 1}, {1, 0}};

void solution();
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solution();
    return 0;
}

pr operator+(pr p1, pr p2) {
	pr ans = {p1.ff +p2.ff, p1.ss+p2.ss};
	return ans;
}


const int MAXN = 805;
const int inf = 1e9;
char A[MAXN][MAXN];
int arr[MAXN][MAXN];
ll n, s;
pr start, destination;
vector<pr> H;
bool vis[MAXN][MAXN];



bool correct(pr cords) {
	return cords.ff <= n && cords.ff >= 1 && 
		cords.ss <= n && cords.ss >= 1 &&
		A[cords.ff][cords.ss] != 'T';
}

void calculateArrival() {
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			arr[i][j] = inf;
		}
	}

	queue<pr> q;
	pr wa = {-1, -1};

	ll tm = 0;
	for (auto val : H) q.push(val);
	q.push(wa);

	while (!q.empty()) {
		pr e = q.front(); q.pop();

		if (e == wa) {
			if (q.size() > 0) q.push(wa);
			tm++;
			continue;
		}

		if (arr[e.ff][e.ss] < tm) continue;
		arr[e.ff][e.ss] = tm;

		for (auto D : move4) {
			pr nkw = D + e;
			if (!correct(nkw) || arr[nkw.ff][nkw.ss] != inf) continue;
			q.push(nkw);
		}
	}
}


bool isValid(ll tm) {
	pr wa = {-1, -1};

	queue<pr> q;
	q.push(start);
	q.push(wa);

	tm++;
	ll t = 0;
	while (!q.empty()) {
		pr e = q.front(); q.pop();

		if (e == wa) {
			if (t >= s) {t = 0; tm++;}
			else t++;

			if (q.size() > 0) q.push(wa);
			
			continue;
		}

		if (vis[e.ff][e.ss] || tm > arr[e.ff][e.ss]) continue;
		vis[e.ff][e.ss] = true;

		if (e == destination && tm < arr[e.ff][e.ss]) return true;

		for (auto D : move4) {
			pr nkw = D + e;
			if (!correct(nkw) || vis[nkw.ff][nkw.ss]) continue;
			q.push(nkw);
		}

	}


	return false;
}


void solution() {
    cin >> n >> s;
    for (int i = 1; i <= n; i++) {
    	for (int j = 1; j <= n; j++) {
    		cin >> A[i][j];
    		if (A[i][j] == 'M') start = {i, j};
    		if (A[i][j] == 'D') destination = {i, j};
    		if (A[i][j] == 'H') H.push_back({i, j});
    	}
    }


    calculateArrival();




    
    ll p = 0, q = 1e7;
    ll ans = -1;
    while (p <= q) {
    	ll mid = (p + q)/2;
    	if (isValid(mid)) {
    		ans = mid;
    		p = mid+1;
    	}else q = mid-1;


    	memset(vis, 0, sizeof(vis));
    }


    cout << ans << endl;


}

• Subtask 1: 4 / 100