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
ihuntuuu: 2022-01-27 08:02:42

Multisource BFS !

fahd_hakem: 2021-10-31 21:37:29

Ac in one go

musky: 2021-08-06 06:26:54

Ac In One Go. Wooow. This is the simplest question. You have to just apply brut force approach.

yasser1110: 2021-07-16 13:49:00

Really nice problem! Good thing it doesn't have tags.

Last edit: 2021-07-16 13:49:27
rec28: 2021-06-15 17:58:23

ac one people should die in peace !!

wslord: 2020-12-29 21:05:32

Loved this question.... Take care, priority queue is not needed ;)

kanishkverma_1: 2020-11-17 17:29:49

If ur having NZEC in java then try the same solution in c++ . Worked like a charm for me. :P

varuntumbe: 2020-10-23 10:01:08

one good optimization is needed in multi source bfs. calculate the no of iterations and compare.

gnomegeek: 2020-08-04 23:42:49

No need to use BFS. Applyting Brute Force works. AC in one go.

satish7978: 2020-07-06 23:14:47

waah. multisource bfs is best.

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