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/* Number of Islands
https://dev.to/rattanakchea/amazons-interview-question-count-island-21h6
Given a 2d grid map of '1's (land) and '0's (water), count 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.
a two dimensional grid map
each element is going to represent a piece of land
1 is land,
0 is water
output a number which is the number of islands
Example 1:
Input:
11110
11010
11000
00000
Output: 1
Example 2:
Input:
11000
11000
00100
00011
Output: 3
I: two dimensional array
O: a single integer; total number of islands
Pseudocode:
OUTER FUNCTION
set count to 0
INNER FUNCTION - flood (col, row)
if the tile is water
return
make tile water(flood tile)
invoke flood on the neighbor coordinates
iterate over the matrix (col, row)
if the current element is a 1
increment count
invoke flood (coordinates for col and row)
Return the count
*/
const islands = (matrixGrid) => {
const matrix = matrixGrid
let counter = 0
const flood = (row, col) => {
if (row < 0 || col < 0) return // Off the map above or left
if (row >= matrix.length || col >= matrix[row].length) return // Off the map below or right
const tile = matrix[row][col]
if (tile !== '1') return
matrix[row][col] = '0'
flood(row + 1, col) // Down
flood(row - 1, col) // Up
flood(row, col + 1) // Right
flood(row, col - 1) // Left
}
for (let row = 0; row < matrix.length; row += 1) {
for (let col = 0; col < matrix[row].length; col += 1) {
const current = matrix[row][col]
if (current === '1') {
flood(row, col)
counter += 1
}
}
}
return counter
}
export { islands }