Submission #550474

#	Time	Username	Problem	Language	Result	Execution time	Memory
550474		Jomnoi	Mecho (IOI09_mecho)	C++17	100 / 100	182 ms	6332 KiB

mecho

#include <bits/stdc++.h>
#define DEBUG false
using namespace std;

const int MAX_N = 810;
const int INF = 1e9 + 7;
const int d[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};

char s[MAX_N][MAX_N];
int db[MAX_N][MAX_N], dm[MAX_N][MAX_N];

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int N, S;
    cin >> N >> S;
    for(int i = 1; i <= N; i++) {
        cin >> (s[i] + 1);
    }

    int sx, sy, ex, ey;
    queue <pair <int, int>> q;
    for(int i = 1; i <= N; i++) {
        for(int j = 1; j <= N; j++) {
            db[i][j] = INF;
            if(s[i][j] == 'H') {
                db[i][j] = 0;
                q.emplace(i, j);
            }
            else if(s[i][j] == 'M') {
                sx = i, sy = j;
            }
            else if(s[i][j] == 'D') {
                ex = i, ey = j;
            }
        }    
    }
    while(!q.empty()) {
        auto [ux, uy] = q.front();
        q.pop();

        for(int i = 0; i < 4; i++) {
            int vx = ux + d[i][0], vy = uy + d[i][1];
            if(vx < 1 or vx > N or vy < 1 or vy > N or s[vx][vy] == 'T' or s[vx][vy] == 'D' or db[vx][vy] != INF) {
                continue;
            }

            db[vx][vy] = db[ux][uy] + 1;
            q.emplace(vx, vy);
        }
    }

    int l = 0, r = N * N, ans = -1;
    while(l <= r) {
        int mid = (l + r) / 2;

        for(int i = 1; i <= N; i++) {
            for(int j = 1; j <= N; j++) {
                dm[i][j] = INF;
            }
        }

        queue <pair <int, int>> q;
        if(db[sx][sy] > mid) {
            q.emplace(sx, sy);
            dm[sx][sy] = 0;
        }
        while(!q.empty()) {
            auto [ux, uy] = q.front();
            q.pop();

            for(int i = 0; i < 4; i++) {
                int vx = ux + d[i][0], vy = uy + d[i][1];
                if(vx < 1 or vx > N or vy < 1 or vy > N or s[vx][vy] == 'T' or dm[vx][vy] != INF) {
                    continue;
                }
                if((dm[ux][uy] + 1) / S >= db[vx][vy] - mid) {
                    continue;
                }

                dm[vx][vy] = dm[ux][uy] + 1;
                q.emplace(vx, vy);
            }
        }

        if(dm[ex][ey] == INF) {
            r = mid - 1;
        }
        else {
            l = mid + 1;
            ans = mid;
        }
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

mecho.cpp: In function 'int main()':
mecho.cpp:85:21: warning: 'ey' may be used uninitialized in this function [-Wmaybe-uninitialized]
   85 |         if(dm[ex][ey] == INF) {
      |            ~~~~~~~~~^
mecho.cpp:85:21: warning: 'ex' may be used uninitialized in this function [-Wmaybe-uninitialized]

• Subtask 1: 100 / 100