31. Number of Islands

Medium

Problem Statement

Given an m x n 2D binary grid grid which represents a map 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.

Examples

1Example 1

Input:

{
  "grid": [
    [
      "1",
      "1",
      "1",
      "1",
      "0"
    ],
    [
      "1",
      "1",
      "0",
      "1",
      "0"
    ],
    [
      "1",
      "1",
      "0",
      "0",
      "0"
    ],
    [
      "0",
      "0",
      "0",
      "0",
      "0"
    ]
  ]
}

Output:

1

2Example 2

Input:

{
  "grid": [
    [
      "1",
      "1",
      "0",
      "0",
      "0"
    ],
    [
      "1",
      "1",
      "0",
      "0",
      "0"
    ],
    [
      "0",
      "0",
      "1",
      "0",
      "0"
    ],
    [
      "0",
      "0",
      "0",
      "1",
      "1"
    ]
  ]
}

Output:

3

3Example 3

Input:

{
  "grid": [
    [
      "0",
      "0",
      "0"
    ],
    [
      "0",
      "0",
      "0"
    ]
  ]
}

Output:

0