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
accesss_denied: 2020-03-28 08:35:43

Ac in one go . Easy multisource bfs question.

sayan_244: 2020-03-22 06:11:10

What's the complexity of the multisource bfs approach?

manish_thakur: 2020-01-15 13:18:36

for those having confusion in input format, you have to input n strings

manuver: 2019-10-28 14:31:12

for who are getting SIGNALABRT (Runtime error) , your solution might be using more memory then available

abba5: 2019-10-08 07:22:41

No need to use BFS, DFS simple logic work in O(n^2)

sonuexpc: 2019-09-28 06:47:41

good question, simple bfs... :) \|/

rishabh121: 2019-08-30 11:19:02


toolatetostart: 2019-06-02 11:58:57

do only using multisource bfs,it is nothing but you have to push all source vertices with distance 0 and all same as djikstra

andyy143: 2019-05-30 11:07:28

@nitishk24 can you share your dp code and logic

abhibrat: 2019-05-22 15:04:56

I am getting WA even after using bfs but can't figure out what test case is causing it. Can someone please look at my code

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