Add JavaScriptNumberOfIslands.md

Author: Superklok

JavaScriptNumberOfIslands.md

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+# JavaScript Number Of Islands
+
+## Challenge:
+
+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. You may assume all four edges of the grid are all surrounded by water.
+
+### 1<sup>st</sup> Example:
+
+`Input: grid = [`
+<br/>
+`["1","1","1","1","0"],`
+<br/>
+`["1","1","0","1","0"],`
+<br/>
+`["1","1","0","0","0"],`
+<br/>
+`["0","0","0","0","0"]`
+<br/>
+`]`
+<br/>
+`Output: 1`
+
+### 2<sup>nd</sup> Example:
+
+`Input: grid = [`
+<br/>
+`["1","1","0","0","0"],`
+<br/>
+`["1","1","0","0","0"],`
+<br/>
+`["0","0","1","0","0"],`
+<br/>
+`["0","0","0","1","1"]`
+<br/>
+`]`
+<br/>
+`Output: 3`
+
+### Constraints:
+
+`m == grid.length`
+<br/>
+`n == grid[i].length`
+<br/>
+`1 <= m, n <= 300`
+<br/>
+`grid[i][j]` is `'0'` or `'1'`.
+
+## Solution:
+
+`const numIslands = (grid) => {`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`let count = 0;`
+<br/>
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`for (let i = 0; i < grid.length; i++) {`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`for (let j = 0; j < grid[0].length; j++) {`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`if (grid[i][j] === '1') {`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`count++;`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`dfs(grid, i,j);`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`}`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`}`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`}`
+<br/>
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`return count;`
+<br/>
+`};`
+<br/>
+<br/>
+`const dfs = (grid, row, col) => {`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`if (row < 0 || row >= grid.length || col < 0 || col >= grid[0].length) {`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`return;`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`}`
+<br/>
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`const value = grid[row][col];`
+<br/>
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`if (value === '1') {`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`grid[row][col] = '#';`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`dfs(grid, row + 1, col);`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`dfs(grid, row - 1, col);`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`dfs(grid, row, col + 1);`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`dfs(grid, row, col - 1);`
+<br/>
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;`}`
+<br/>
+`};`
+<br/>
+<br/>