Number of Closed Islands

arraydepth-first searchbreadth-first search

Problem Statement

Given a 2D grid consists of 0s (land) and 1s (water). An island is a maximal 4-directionally connected group of 0 s and a closed island is an island totally (all left, top, right, bottom) surrounded by 1s.

Return the number of closed islands .

Examples

Example 1

Input: grid = [[1,1,1,1,1,1,1,0],[1,0,0,0,0,1,1,0],[1,0,1,0,1,1,1,0],[1,0,0,0,0,1,0,1],[1,1,1,1,1,1,1,0]]
Output: 2
Islands in gray are closed because they are completely surrounded by water (group of 1s).

Example 2

Input: grid = [[0,0,1,0,0],[0,1,0,1,0],[0,1,1,1,0]]
Output: 1

Example 3

Input: grid = [[1,1,1,1,1,1,1],
  [1,0,0,0,0,0,1],
  [1,0,1,1,1,0,1],
  [1,0,1,0,1,0,1],
  [1,0,1,1,1,0,1],
  [1,0,0,0,0,0,1],
 [1,1,1,1,1,1,1]]
Output: 2

Constraints

1 <= grid.length, grid[0].length <= 100

0 <= grid[i][j] <=1

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicDepth-First Search