Submission #893148

#	Time	Username	Problem	Language	Result	Execution time	Memory
893148		vanea	Tracks in the Snow (BOI13_tracks)	C++14	97.81 / 100	896 ms	1048576 KiB

tracks

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int label = 1, n, m;
const int mxN = 4e3+10;
const int mxN1 = 5e6+10;

vector<int> adj[mxN1];
bool vis[mxN][mxN];
char matrix[mxN][mxN];
int idx[mxN][mxN], d[mxN1];

vector<int> xy = {1, 0, -1, 0}, yx = {0, 1, 0, -1};

void dfs(int i, int j) {
    char c = matrix[i][j];
    idx[i][j] = label;
    vis[i][j] = true;
    for(int k = 0; k < 4; k++) {
        int a = i + xy[k], b = j + yx[k];
        if(a < 0 || a >= n || b < 0 || b >= m) continue;
        if(matrix[a][b] == '.') continue;
        if(matrix[a][b] == c) {
            if(!vis[a][b]) dfs(a, b);
        }
        else {
            if(vis[a][b]) {
                adj[label].push_back(idx[a][b]);
                adj[idx[a][b]].push_back(label);
            }
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            cin >> matrix[i][j];
        }
    }
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(matrix[i][j] != '.' && !vis[i][j]) {
                dfs(i, j);
                ++label;
            }
        }
    }
    queue<int> q;
    q.push(1);
    d[1] = 1;
    int ans = 0;
    while(!q.empty()) {
        auto node = q.front();
        q.pop();
        ans = max(ans, d[node]);
        for(auto it : adj[node]) {
            if(d[it] == 0) {
                d[it] = d[node]+1;
                q.push(it);
            }
        }
    }
    cout << ans;
}

• Subtask 1: 30 / 30
• Subtask 2: 67.8125 / 70