Submission #971341

#	Time	Username	Problem	Language	Result	Execution time	Memory
971341		Bodisha	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	1426 ms	679992 KiB

tracks

#include <bits/stdc++.h>
#define MAX_D 4000
#define MAX_D 4000

using namespace std;

int h, w;
char meadow[MAX_D][MAX_D];
int component[MAX_D][MAX_D];
vector<int> graph[MAX_D * MAX_D];
int d[MAX_D * MAX_D];
queue<int> q;

void floodfill(int x, int y, int cmp) {
    stack<pair<int, int>> s;
    component[x][y] = cmp;
    s.push({x, y});
    while(!s.empty()) {
        pair<int, int> curr = s.top();
        s.pop();
        if(curr.first + 1 < h && meadow[curr.first][curr.second] == meadow[curr.first + 1][curr.second] && component[curr.first + 1][curr.second] == 0) {
            component[curr.first + 1][curr.second] = cmp;
            s.push({curr.first + 1, curr.second});
        }
        if(curr.first - 1 >= 0 && meadow[curr.first][curr.second] == meadow[curr.first - 1][curr.second] && component[curr.first - 1][curr.second] == 0) {
            component[curr.first - 1][curr.second] = cmp;
            s.push({curr.first - 1, curr.second});
        }
        if(curr.second + 1 < w && meadow[curr.first][curr.second] == meadow[curr.first][curr.second + 1] && component[curr.first][curr.second + 1] == 0) {
            component[curr.first][curr.second + 1] = cmp;
            s.push({curr.first, curr.second + 1});
        }
        if(curr.second - 1 >= 0 && meadow[curr.first][curr.second] == meadow[curr.first][curr.second - 1] && component[curr.first][curr.second - 1] == 0) {
            component[curr.first][curr.second - 1] = cmp;
            s.push({curr.first, curr.second - 1});
        }
    }
}

int main() {
    string tmps;
    cin >> h >> w;
    for(int i = 0; i < h; i++) {
        cin >> tmps;
        for(int j = 0; j < w; j++) {
            meadow[i][j] = tmps[j];
        }   
    }
    int cnt = 1;
    for(int i = 0; i < h; i++) {
        for(int j = 0; j < w; j++) {
            if(component[i][j] == 0 && meadow[i][j] != '.') {
                floodfill(i, j, cnt);
                cnt++;
            }
        }
    }
    for(int i = 0; i < h; i++) {
        for(int j = 0; j < w; j++) {
            if(meadow[i][j] == '.') {
                continue;
            }
            if(i + 1 < h && meadow[i + 1][j] != '.' && component[i + 1][j] != component[i][j]) {
                graph[component[i + 1][j]].push_back(component[i][j]);
                graph[component[i][j]].push_back(component[i + 1][j]);
            }
            if(i - 1 >= 0 && meadow[i - 1][j] != '.' && component[i - 1][j] != component[i][j]) {
                graph[component[i - 1][j]].push_back(component[i][j]);
                graph[component[i][j]].push_back(component[i - 1][j]);
            }  
            if(j + 1 < w && meadow[i][j + 1] != '.' && component[i][j + 1] != component[i][j]) {
                graph[component[i][j + 1]].push_back(component[i][j]);
                graph[component[i][j]].push_back(component[i][j + 1]);
            }  
            if(j - 1 >= 0 && meadow[i][j - 1] != '.' && component[i][j - 1] != component[i][j]) {
                graph[component[i][j - 1]].push_back(component[i][j]);
                graph[component[i][j]].push_back(component[i][j - 1]);
            }     
        }
    }
    fill(d, d + cnt, -1);
    d[component[0][0]] = 0;
    q.push(component[0][0]);
    while(!q.empty()) {
        int curr_node = q.front();
        q.pop();
        for(auto iter : graph[curr_node]) {
            if(d[iter] == -1) {
                d[iter] = d[curr_node] + 1;
                q.push(iter);
            }
        }
    }
    int ans = 1;
    for(int i = 0; i < cnt; i++) {
        ans = max(ans, d[i] + 1);
    }
    cout << ans;
    return 0;
}

• Subtask 1: 30 / 30
• Subtask 2: 70 / 70