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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
agspoj: 2015-09-22 08:58:27

I finally solved it. If someone is interested this is the testcase which coused problem: "1\n4 6\n100001\n100001\n100001\n100001".

Last edit: 2015-10-08 14:46:13
kartikay singh: 2015-09-05 08:44:02

queue ==> AC 0.19s
lists ==> severals WA .dont know why :(

Last edit: 2015-09-05 08:49:30
[Mayank Pratap]: 2015-08-31 16:31:31

Used std::queue AC 0.49s
Used std::list AC 2.2s
Question clears many concepts....

anshal dwivedi: 2015-08-29 06:04:03

yo!AC ..!using simple bfs

Last edit: 2015-08-29 07:12:31
epsilon: 2015-08-27 17:27:46

brute_force woks wondering why (time==3.34sec)!!!!!!!!!!!!!
using bfs(time==0.04sec)

Last edit: 2015-08-27 19:11:55
ganpya: 2015-08-13 06:49:57

BFS on whilte Pixel vs BFS on Black Pixel : AC vs TLE

ALi Ibrahim: 2015-08-03 00:13:50

easy problem, simple bfs, First Accepted in 0.24 :)

monkz: 2015-07-31 17:56:57

will O(n^3) solution work??

Vikrant Singh: 2015-07-26 18:19:57

Brute Force, really ?

Ashish: 2015-07-08 15:21:58

Can be done by simple brute force! I will try doing it by BFS though.

Added by:Piotr Ɓowiec
Time limit:4s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel Pentium G860 3GHz)
Resource:6th Polish Olympiad in Informatics, stage 2