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| 1 | +/* |
| 2 | +*************************** |
| 3 | +* * |
| 4 | +* Author: Swaraj Deep * |
| 5 | +* * |
| 6 | +*************************** |
| 7 | +*/ |
| 8 | + |
| 9 | +#include <iostream> |
| 10 | +#include <vector> |
| 11 | +#include <queue> |
| 12 | + |
| 13 | +using namespace std; |
| 14 | + |
| 15 | +// Function to check whether cell[x][y] is valid or not |
| 16 | +bool is_valid(int x, int y, vector<vector<bool>> &visited) |
| 17 | +{ |
| 18 | + int n = visited.size(), m = visited.size(); |
| 19 | + if (x < 1 || x >= n || y < 1 || y >= m || visited[x][y]) |
| 20 | + { |
| 21 | + return false; |
| 22 | + } |
| 23 | + return true; |
| 24 | +} |
| 25 | + |
| 26 | +// Considering only adjacent cells as edges. Can also be extended for all eight cells |
| 27 | +vector<int> dx{-1, 0, 1, 0}; |
| 28 | +vector<int> dy{0, 1, 0, -1}; |
| 29 | + |
| 30 | +void bfs_on_grid(int source_x, int source_y, vector<vector<bool>> &visited, vector<vector<int>> &distance) |
| 31 | +{ |
| 32 | + queue<pair<int, int>> q; |
| 33 | + q.push({source_x, source_y}); // Inserting into the queue the current cell |
| 34 | + visited[source_x][source_y] = true; |
| 35 | + distance[source_x][source_y] = 0; // Distance of source_x and source_y is zero |
| 36 | + while (!q.empty()) |
| 37 | + { |
| 38 | + int current_x = q.front().first; |
| 39 | + int current_y = q.front().second; |
| 40 | + q.pop(); |
| 41 | + // Checking all adjacent sides |
| 42 | + for (int i = 0; i < 4; ++i) |
| 43 | + { |
| 44 | + if (is_valid(current_x + dx[i], current_y + dy[i], visited)) |
| 45 | + { |
| 46 | + int new_x = current_x + dx[i]; |
| 47 | + int new_y = current_y + dy[i]; |
| 48 | + distance[new_x][new_y] = distance[current_x][current_y] + 1; |
| 49 | + visited[new_x][new_y] = true; |
| 50 | + q.push({new_x, new_y}); |
| 51 | + } |
| 52 | + } |
| 53 | + } |
| 54 | +} |
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