sadie100: number of islands solution

Author: sadie100

number-of-islands/sadie100.ts

@@ -0,0 +1,45 @@
+/*
+m x n visited 이중배열을 만들고 grid를 탐색,
+visited false면서 1값이 있는 타일이 있으면 dfs로 상하좌우를 탐색, visited true로 만든 뒤 result+=1한다
+탐색이 마치면 result를 리턴한다
+
+시간복잡도 : O(M + N)
+공간복잡도 : O(M + N) - visited
+*/
+
+const dx = [0, 1, -1, 0]
+const dy = [1, 0, 0, -1]
+
+function numIslands(grid: string[][]): number {
+  const visited = Array.from({ length: grid.length }, () =>
+    new Array(grid[0].length).fill(false),
+  )
+  let result = 0
+
+  function search(row: number, col: number) {
+    visited[row][col] = true
+
+    for (let i = 0; i < 4; i++) {
+      const newRow = row + dx[i]
+      const newCol = col + dy[i]
+
+      if (newRow < 0 || newRow >= grid.length) continue
+      if (newCol < 0 || newCol >= grid[0].length) continue
+
+      if (visited[newRow][newCol] === false && grid[newRow][newCol] === '1') {
+        search(newRow, newCol)
+      }
+    }
+  }
+
+  for (let i = 0; i < grid.length; i++) {
+    for (let j = 0; j < grid[0].length; j++) {
+      if (visited[i][j] === false && grid[i][j] === '1') {
+        search(i, j)
+        result += 1
+      }
+    }
+  }
+
+  return result
+}