BITMAP - Bitmap

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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:



Write a program which:

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


The number of test cases t 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.


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.


Sample input:
3 4

Sample output:
3 2 1 0
2 1 0 0
1 0 0 1

hide comments
ashishsb95: 2017-01-21 16:00:38

the trick was not to use multiple bfs calls :/

aditya9125: 2017-01-06 10:31:21

Nice one .Do try it!

up79: 2016-12-25 17:09:05

BFS did it !
superb question ! must do <3

manish556: 2016-12-08 08:31:41

Brute force worked..!!
Time limit is huge..

hamjosh1: 2016-10-07 12:38:10

:D enjoyed

alaa_alrayes96: 2016-10-02 12:16:37

recursion may not pass

akshayvenkat: 2016-09-17 22:19:09

No need to use bfs. Brute forced my way to 0.06s B|

vikikkdi: 2016-09-16 08:49:32

Last edit: 2016-09-16 08:49:45
Vinay Sharma: 2016-09-01 15:56:10

Why does it give SIGSEGV ?

imwrkhrd: 2016-08-28 22:46:47

n/m seems to be bigger than 182

Added by:Piotr Ɓowiec
Time limit:4s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Resource:6th Polish Olympiad in Informatics, stage 2