number-of-islands solution

Author: lhc0506

number-of-islands/lhc0506.js

@@ -0,0 +1,42 @@
+/**
+ * @param {character[][]} grid
+ * @return {number}
+ */
+var numIslands = function(grid) {
+  const m = grid.length;
+  const n = grid[0].length;
+  const visited = Array.from(new Array(m), () => new Array(n).fill(false));
+  const directions = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+
+  let islandCount = 0;
+
+  for (let i = 0; i < m; i++) {
+      for (let j = 0; j < n; j++) {
+          if (grid[i][j] === '1' && !visited[i][j]) {
+              const queue = [[i, j]];
+              visited[i][j] = true;
+
+              while (queue.length) {
+                  const [y, x] = queue.shift();
+
+                  for (const [dy, dx] of directions) {
+                      const newY = y + dy;
+                      const newX = x + dx;
+
+                      if (newY >= 0 && newY < m && newX >= 0 && newX < n && grid[newY][newX] === '1' && !visited[newY][newX]) {
+                          visited[newY][newX] = true;
+                          queue.push([newY, newX]);
+                      }
+                  }
+              }
+
+              islandCount += 1;
+          }
+      }
+  }
+
+  return islandCount;
+};
+
+// 시간복잡도: O(m * n)
+// 공간복잡도: O(m * n)