Dott

Gets the distance to the nearest white pixel

What It Does

reads the description of the bitmap from the standard input;
for each pixel, computes the distance to the nearest white;
writes the results to the standard output.

Installation and Usage
Approach
Task
Input
Output

Installation and Usage

Prerequisites: Node.js (>=12.0.0)

Clone the repo and enter the project directory and then:

$ npm install && npm run build && npm link

And now execute help to see what you can do with it:

$ dott --help

Be aware that usually program will start in execution mode. Like:

$ dott
1
3 4
0001
0011
0110

<Press Enter>

3 2 1 0
2 1 0 0
1 0 0 1

Details

Approach

It uses bfs coupled with a bit of maze pathfinding algo without backtracking though, at least this is how I explained it to myself, haha.

See Distance transform article.

Task

There is given a rectangular bitmap of size n*m. Each pixel of the bitmap is either white or black, but at least one is white. The pixel in i-th line and j-th column is called the pixel (i,j). The distance between two pixels p1=(i1,j1) and p2=(i2,j2) is defined as d(p1,p2)=|i1-i2|+|j1-j2|.

Input

The number of test cases t (1≤t≤1000) is in the first line of input, then t test cases follow separated by an empty line. In the first line of each test case there is a pair of integer numbers n, m separated by a single space, 1<=n <=182, 1<=m<=182. In each of the following n lines of the test case exactly one zero-one word of length m, the description of one line of the bitmap, is written. On the j-th position in the line (i+1), 1 <= i <= n, 1 <= j <= m, is 1 if, and only if the pixel (i,j) is white.

Output

In the i-th line for each test case, 1<=i<=n, there should be written m integers f(i,1),...,f(i,m) separated by single spaces, where f(i,j) is the distance from the pixel (i,j) to the nearest white pixel.

markelog/dott