Number of Islands

Problem Description Given an m x n grid of '1's (land) and '0's (water), return the number of islands. 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. Input A 2D grid map of '1's (land) and '0's (water). Output An integer representing the number of islands. Test Cases Input: [ ['1', '1', '0', '0', '0'], ['1', '1', '0', '0', '0'], ['0', '0', '1', '0', '0'], ['0', '0', '0', '1', '1'] ] Output: 3 Input: [ ['1', '0', '0'], ['0', '1', '1'], ['0', '0', '0'] ] Output: 2 Input: [ ['1', '1', '1'], ['1', '0', '1'], ['1', '1', '1'] ] Output: 1 Constraints The grid may contain at most 1000 cells. Example Input 111001",