Given an m x n 2D grid map of '1’s which represents land and '0’s that represents water return the number of islands (surrounded by water and formed by connecting adjacent lands in 2 directions - vertically or horizontally).

Given an m x n 2D grid map of '1’s which represents land and '0’s

1.	Given an m x n 2D grid map of '1’s which represents land and '0’s that represents water return the number of islands (surrounded by water and formed by connecting adjacent lands in 2 directions - vertically or horizontally).
Answer» Assume that the boundary cases - which are all four edges of the grid are surrounded by water. Constraints are: m == grid.length n == grid[i].length 1 <= m, n <= 300 grid[i][j] can only be ‘0’ or ‘1’. Example: Input: grid = [ [“1” , “1” , “1” , “0” , “0”], [“1” , “1” , “0” , “0” , “0”], [“0” , “0” , “1” , “0” , “1”], [“0” , “0” , “0” , “1” , “1”] ] Output: 3 class InterviewBit { public int numberOfIslands(char[][] grid) { if(grid==null \|\| grid.length==0\|\|grid[0].length==0) return 0; int m = grid.length; int n = grid[0].length; int count=0; for(int i=0; i<m; i++){ for(int j=0; j<n; j++){ if(grid[i][j]=='1'){ count++; mergeIslands(grid, i, j); } } } return count; } public void mergeIslands(char[][] grid, int i, int j){ int m=grid.length; int n=grid[0].length; if(i<0\|\|i>=m\|\|j<0\|\|j>=n\|\|grid[i][j]!='1') return; grid[i][j]='X'; mergeIslands(grid, i-1, j); mergeIslands(grid, i+1, j); mergeIslands(grid, i, j-1); mergeIslands(grid, i, j+1); } }