Add number-of-islands solution in TS

Author: Jeehay28

number-of-islands/Jeehay28.ts

@@ -0,0 +1,41 @@
+// TC: O(n), where N = total number of cells = m * n
+// SC: O(n)
+
+function numIslands(grid: string[][]): number {
+  const sink = (row: number, col: number) => {
+    visited[row][col] = true;
+
+    const dirs = [
+      [row - 1, col],
+      [row + 1, col],
+      [row, col - 1],
+      [row, col + 1],
+    ];
+
+    for (const dir of dirs) {
+      const [r, c] = dir;
+
+      if (r >= 0 && r < grid.length && c >= 0 && c < grid[0].length) {
+        if (!visited[r][c] && grid[r][c] === "1") {
+          sink(r, c);
+        }
+      }
+    }
+  };
+
+  let count = 0;
+  const visited: boolean[][] = Array.from({ length: grid.length }, () =>
+    Array(grid[0].length).fill(false)
+  );
+
+  for (let i = 0; i < grid.length; i++) {
+    for (let j = 0; j < grid[0].length; j++) {
+      if (!visited[i][j] && grid[i][j] === "1") {
+        count++;
+        sink(i, j); // // Sink all connected neighboring land cells
+      }
+    }
+  }
+
+  return count;
+}