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Problem

Submissions

COUNT ISLANDS

Contributed by

Abhishek Gupta

Last Updated: 23 Feb, 2023

Medium

0/80

Avg time to solve 40 mins

Success Rate 40 %

0 upvotes

Problem Statement

You are given an empty 2D binary 'GRID' of size ‘N’ x 'M' The 'GRID' represents a map where 0's represent water and 1's represent land. Initially, all the cells of the 'GRID' are water cells (i.e., all the cells are 0's).

We may perform an add land operation which turns the water at position into a land. You are given an array 'POSITIONS' of size ‘K’ where POSITIONS[i] = [Ri, Ci] is the position (Ri, Ci) at which we should operate the ith operation.

Return an array of integers answer where ‘ANSWER[i]’ is the number of islands after turning the cell (‘Ri’, ‘Ci’) into a land.

An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the 'GRID' are all surrounded by water.

Example:

Input: ‘M’ = 3, 'N' = 3, 'POSITIONS' = [ [ 0,0 ], [ 0,1 ], [ 1,2 ], [ 2,1 ] ]

Output: [1, 1, 2, 3]

Initially, the 2d  'GRID' is filled with water.
- Operation #1: addLand(0, 0) turns the water at  ‘GRID[0][0]’ into a land. We have 1 island.
- Operation #2: addLand(0, 1) turns the water at  ‘GRID[0][1]’ into a land. We still have 1 island.
- Operation #3: addLand(1, 2) turns the water at  'GRID[1][2]’ into a land. We have 2 islands.
- Operation #4: addLand(2, 1) turns the water at  'GRID[2][1]’ into a land. We have 3 islands.

Detailed explanation ( Input/output format, Notes, Images )

Input Format :

The first line contains ‘T’, denoting the number of test cases.    

The first line of each test case contains two integers, ‘N’ and ‘M’, denoting the number of rows and columns in the  'GRID'.

The second line of each test case contains an integer ‘K’ denoting the size of ‘POSITION’ array.

Each of the next ‘K’ lines contains two space-separated integers denoting the (‘Ri’, ‘Ci’) of ‘POSITION[i]’.

Output format :

For each test case, return the array of integers as described in the problem statement.

Note :

You don't need to print anything. It has already been taken care of. Just implement the given function.

Constraints :

1 <= T <= 10
1 <= M, N, K <= 100
0 <= Ri< m
0 <= Ci < n

Time Limit: 1 sec

Sample Input 1 :

##### Sample Output 1 :

 1 1 1 
 1 2 1

Explanation Of Sample Input 1 :

For the first test case:-
- Operation #1: addLand(0, 0) turns the water at  ‘GRID’[0][0] into a land. We have 1 island,  [( 0, 0)].
- Operation #2: addLand(0, 1) turns the water at  ‘GRID’[0][1] into a land. We still have 1     island,  [ ( 0, 0) , ( 0, 1 ) ].
- Operation #3: addLand(0, 2) turns the water at  'GRID'[1][2] into a land. We still have 1 island,  [ ( 0, 0) , ( 0, 1 ), ( 0, 2 ) ].


For the second test case:-
   - Operation #1: addLand(0, 0) turns the water at  ‘GRID’[0][0] into a land. We have 1 island, [ ( 0, 0 ) ].
- Operation #2: addLand(0, 2) turns the water at  ‘GRID’[0][1] into a land. We still have 2    islands, [ ( 0, 0 ) ] and [ ( 0, 2 ) ].
- Operation #3: addLand(0, 2) turns the water at  'GRID'[1][2] into a land. We have 1 island,  [ ( 0, 0) , ( 0, 1 ), ( 0, 2 ) ].

Sample Input 2 :

Sample Output 2 :

 1 1 2 3 
 1 1 2 2

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