#include <iostream>
#include <queue>
#include <tuple>
using namespace std;
int H, W;
char grid[4000][4000];
int visited[4000][4000];
int main() {
cin >> H >> W;
for (int i = 0; i < H; ++i) {
string row;
cin >> row;
for (int j = 0; j < W; ++j) {
grid[i][j] = row[j];
}
}
deque<tuple<int, int>> q;
q.push_front({0, 0});
visited[0][0] = 1;
while (!q.empty()) {
auto [i, j] = q.front();
q.pop_front();
if (i > 0 && !visited[i - 1][j]) {
if (grid[i - 1][j] == grid[i][j]) {
visited[i - 1][j] = visited[i][j];
q.push_front({i - 1, j});
} else if (grid[i - 1][j] != '.') {
visited[i - 1][j] = visited[i][j] + 1;
q.push_back({i - 1, j});
}
}
if (i < H - 1 && !visited[i + 1][j]) {
if (grid[i + 1][j] == grid[i][j]) {
visited[i + 1][j] = visited[i][j];
q.push_front({i + 1, j});
} else if (grid[i + 1][j] != '.') {
visited[i + 1][j] = visited[i][j] + 1;
q.push_back({i + 1, j});
}
}
if (j > 0 && !visited[i][j - 1]) {
if (grid[i][j - 1] == grid[i][j]) {
visited[i][j - 1] = visited[i][j];
q.push_front({i, j - 1});
} else if (grid[i][j - 1] != '.') {
visited[i][j - 1] = visited[i][j] + 1;
q.push_back({i, j - 1});
}
}
if (j < W - 1 && !visited[i][j + 1]) {
if (grid[i][j + 1] == grid[i][j]) {
visited[i][j + 1] = visited[i][j];
q.push_front({i, j + 1});
} else if (grid[i][j + 1] != '.') {
visited[i][j + 1] = visited[i][j] + 1;
q.push_back({i, j + 1});
}
}
}
int answer = 0;
for (int i = 0; i < H; ++i) {
answer = max(answer, *max_element(visited[i], visited[i] + W));
}
cout << answer << '\n';
}
Compilation message
tracks.cpp: In function 'int main()':
tracks.cpp:26:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
26 | auto [i, j] = q.front();
| ^
tracks.cpp:69:31: error: 'max_element' was not declared in this scope
69 | answer = max(answer, *max_element(visited[i], visited[i] + W));
| ^~~~~~~~~~~
