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
sipian: 2017-06-03 22:19:12

a good question

botstar: 2017-05-29 22:43:09

got 15 TLEs....mistake == using iosbase and scnf together...fkcu...c++..

akash619j: 2017-05-29 09:20:25

Little tricky even after you know its bfs!

s407189: 2017-04-03 12:01:56

it could use some more examples. Does it even test for more than one data set ?

vengatesh15: 2017-03-27 12:35:45

AC in 1 go using BFS

nilabja16180: 2017-02-19 16:51:59

Awesome 0 1 BFS implementation

Last edit: 2017-02-19 16:52:09
scorpion_ajay: 2017-02-14 12:42:59

must try, learned a lot from this single problem :)

manish_hacked: 2017-02-06 05:40:43

Very good question for learning bfs!!
don't try brute force method ,try to solve by using bfs!!

nikunjsoni: 2017-01-25 15:35:48

Good Question to learn BFS on matrix...
Deserves my upvote

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

the trick was not to use multiple bfs calls :/

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