Given a matrix that is filled with ‘O’, ‘G’, and ‘W’ where ‘O’ represents open space, ‘G’ represents guards and ‘W’ represents walls in a Bank. Replace all of the O’s in the matrix with their shortest distance from a guard, without being able to go through any walls. Also, replace the guards with 0 and walls with -1 in output matrix.
Expected Time complexity is O(MN) for a M x N matrix.
O ==> Open Space G ==> Guard W ==> Wall Input: O O O O G O W W O O O O O W O G W W W O O O O O G Output: 3 3 2 1 0 2 -1 -1 2 1 1 2 3 -1 2 0 -1 -1 -1 1 1 2 2 1 0
The idea is to do BFS. We first enqueue all cells containing the guards and loop till queue is not empty. For each iteration of the loop, we dequeue the front cell from the queue and for each of its four adjacent cells, if cell is an open area and its distance from guard is not calculated yet, we update its distance and enqueue it. Finally after BFS procedure is over, we print the distance matrix.
Below is C++ implementation of above idea –
3 3 2 1 0 2 -1 -1 2 1 1 2 3 -1 2 0 -1 -1 -1 1 1 2 2 1 0
This article is contributed by Aditya Goel. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
- Shortest distance between two cells in a matrix or grid
- Find shortest safe route in a path with landmines
- Some interesting shortest path questions | Set 1
- Multistage Graph (Shortest Path)
- Dijkstra’s shortest path algorithm using set in STL
- Shortest path in a Binary Maze
- Shortest path in an unweighted graph
- Shortest Path using Meet In The Middle
- Dijkstra's shortest path with minimum edges
- 0-1 BFS (Shortest Path in a Binary Weight Graph)
- Dijkstra's Shortest Path Algorithm using priority_queue of STL
- Shortest Path in Directed Acyclic Graph
- Johnson's algorithm for All-pairs shortest paths
- Printing Paths in Dijkstra's Shortest Path Algorithm
- Number of shortest paths in an unweighted and directed graph