Submission #604187

#	Time	Username	Problem	Language	Result	Execution time	Memory
604187		jackkkk	Tracks in the Snow (BOI13_tracks)	C++11	65 / 100	2114 ms	598360 KiB

tracks

// EMPTY
// 

#include <stdio.h>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <map>
#include <array>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <algorithm>
#include <stdlib.h>
#include <math.h>
#include <list>
#include <float.h>
#include <climits>
using namespace std;


void quit() {
  cout.flush();
  exit(0);
}
char grid[4002][4002];
map<int, unordered_set<int>> adj;
map<pair<int, int>, int> id;
int curr_id = 1;
deque <pair<int, int>> dq;
vector<pair<int, int>> gto = {{1,0},{0,1},{-1,0},{0,-1}};
void flood(int a, int b){
  id[{a,b}]=curr_id;
  char c = grid[a][b];
  grid[a][b]='.';
  dq.clear();
  dq.emplace_back(a, b);
  while(!dq.empty()){
    auto curr = dq.front();
    dq.pop_front();
    for(auto to : gto){
      pair<int, int> nxt = {curr.first+to.first, curr.second+to.second};
      if(grid[nxt.first][nxt.second] == c){
        id[nxt]=curr_id;
        grid[nxt.first][nxt.second] = '.';
        dq.push_back(nxt);
      }
      if(id[nxt]!=0 && id[nxt] != curr_id){
        adj[id[nxt]].insert(curr_id);
        adj[curr_id].insert(id[nxt]);
      }
    }
  }
  curr_id++;
}
int main(void){
  //freopen("qwer.in", "r", stdin);
  //freopen("qwer.out", "w", stdout);
  ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  int n, m; cin >> n >> m;
  for(int i = 0; i < 4002; i++){
    for(int j = 0; j < 4002; j++){
      grid[i][j]='.';
    }
  }
  for(int i = 1; i <= n; i++){
    string s; cin >> s;
    for(int j = 1; j <= m; j++){
      grid[i][j]=s[j-1];
    }
  }
  for(int i = 1; i <= n; i++){
    for(int j = 1; j <= m; j++){
      if(grid[i][j] != '.'){
        flood(i, j);
      }
    }
  }
  deque <int> dq;
  dq.push_back(1);
  vector <int> dist(curr_id, 1e9);
  dist[1]=0;
  while(!dq.empty()){
    int curr = dq.front();
    dq.pop_front();
    for(int nxt : adj[curr]){
      if(dist[curr]+1 < dist[nxt]){
        dist[nxt]=dist[curr]+1;
        dq.push_back(nxt);
      }
    }
  }

  int ans = 0;
  for(int i = 1; i < curr_id; i++){
    ans = max(ans, dist[i]);
  }
  cout << ans+1 << "\n";
  quit();
}

• Subtask 1: 30 / 30
• Subtask 2: 35 / 70