Submission #625160

#	Time	Username	Problem	Language	Result	Execution time	Memory
625160		Stavab	Tracks in the Snow (BOI13_tracks)	C++14	80.31 / 100	2128 ms	1048576 KiB

tracks

#include <iostream>
#include <vector>
#include <utility>
#include <queue>

using namespace std;

vector<vector<char>> field;
int h, w, answer = 1;
vector<int> father, chainSize, turn, put;
vector<vector<pair<int, int>>> points;

int find(int n)
{
    if(father[n] != n)
        father[n] = find(father[n]);
        
    return father[n];
}

void join(int a, int b)
{
    a = find(a);
    b = find(b);
    
    if(a == b)
        return;
    
    if(chainSize[a] < chainSize[b])
        swap(a, b);
    
    father[b] = a;
    chainSize[a] += chainSize[b];
}

int main()
{
    scanf("%d %d", &h, &w);
    
    field.assign(h, vector<char>(w));
    father.assign(h*w, 0);
    chainSize.assign(h*w, 1);
    turn.assign(h*w, 0);
    points.assign(h*w, vector<pair<int, int>>());
    put.assign(h*w, 0);
    
    for(int i = 0; i < h; i++)
    {
        for(int j = 0; j < w; j++)
        {
            scanf(" %c", &field[i][j]);
            father[i*w + j] = i*w + j;
            
            if(field[i][j] == '.')
                continue;
            
            if(i != 0)
            {
                if(field[i - 1][j] == field[i][j])
                    join(i*w + j, (i - 1)*w + j);
            }
            if(j != 0)
            {
                if(field[i][j - 1] == field[i][j])
                    join(i*w + j, i*w + j - 1);
            }
        }
    }
    
    for(int i = 0; i < h; i++)
    {
        for(int j = 0; j < w; j++)
            points[find(i*w + j)].push_back(make_pair(i, j));
    }
    turn[find(0)] = 1;
    
    queue<int> q;
    q.push(find(0));
    put[find(0)] = 1;
    
    while(!q.empty())
    {
        int cur = q.front();
        answer = max(answer, turn[cur]);
        
        for(int i = 0; i < points[cur].size(); i++)
        {
            int a = points[cur][i].first;
            int b = points[cur][i].second;
            
            if(a != 0)
            {
                if(field[a - 1][b] != '.' && find((a - 1)*w + b) != cur)
                {
                    if(!put[find((a - 1)*w + b)])
                    {
                        turn[find((a - 1)*w + b)] = turn[cur] + 1;
                        q.push(find((a - 1)*w + b));
                        put[find((a - 1)*w + b)] = 1;
                    }
                }
            }
            if(b != 0)
            {
                if(field[a][b - 1] != '.' && find(a*w + b - 1) != cur)
                {
                    if(!put[find(a*w + b - 1)])
                    {
                        turn[find(a*w + b - 1)] = turn[cur] + 1;
                        q.push(find(a*w + b - 1));
                        put[find(a*w + b - 1)] = 1;
                    }
                }
            }
            if(a != h - 1)
            {
                if(field[a + 1][b] != '.' && find((a + 1)*w + b) != cur)
                {
                    if(!put[find((a + 1)*w + b)])
                    {
                        turn[find((a + 1)*w + b)] = turn[cur] + 1;
                        q.push(find((a + 1)*w + b));
                        put[find((a + 1)*w + b)] = 1;
                    }
                }
            }
            if(b != w - 1)
            {
                if(field[a][b + 1] != '.' && find(a*w + b + 1) != cur)
                {
                    if(!put[find(a*w + b + 1)])
                    {
                        turn[find(a*w + b + 1)] = turn[cur] + 1;
                        q.push(find(a*w + b + 1));
                        put[find(a*w + b + 1)] = 1;
                    }
                }
            }
        }
               
        q.pop();
    }
    
    printf("%d\n", answer);
    
    return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'int main()':
tracks.cpp:86:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   86 |         for(int i = 0; i < points[cur].size(); i++)
      |                        ~~^~~~~~~~~~~~~~~~~~~~
tracks.cpp:38:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |     scanf("%d %d", &h, &w);
      |     ~~~~~^~~~~~~~~~~~~~~~~
tracks.cpp:51:18: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |             scanf(" %c", &field[i][j]);
      |             ~~~~~^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 50.3125 / 70