[Leetcode - Medium] Shortest Bridge

bangdori/Shortest Bridge.js

@@ -0,0 +1,89 @@
+const WATER = 0;
+const ISLAND = 1;
+const ISLAND2 = 2;
+const DIRS = [
+  [-1, 0],
+  [1, 0],
+  [0, -1],
+  [0, 1],
+];
+
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+var shortestBridge = function (grid) {
+  const rows = grid.length;
+  const cols = grid[0].length;
+
+  let queue = [];
+
+  const exploreIslandDFS = (row, col) => {
+    if (grid[row][col] === ISLAND2) return;
+
+    grid[row][col] = ISLAND2;
+    queue.push([row, col]);
+
+    for (let [dx, dy] of DIRS) {
+      const nextRow = row + dx;
+      const nextCol = col + dy;
+
+      if (
+        isValidCoords(nextRow, nextCol) &&
+        grid[nextRow][nextCol] === ISLAND
+      ) {
+        exploreIslandDFS(nextRow, nextCol);
+      }
+    }
+  };
+
+  const connectIslandBFS = () => {
+    /**
+     * 이동 거리를 나타내는 변수
+     * ISLAND와 차이를 두기 위해 음수값으로 적용
+     */
+    let distance = -1;
+    let currentQueue = queue;
+
+    while (currentQueue.length > 0) {
+      queue = [];
+
+      for (const [row, col] of currentQueue) {
+        for (const [dx, dy] of DIRS) {
+          const nextRow = row + dx;
+          const nextCol = col + dy;
+
+          if (isValidCoords(nextRow, nextCol)) {
+            if (grid[nextRow][nextCol] === WATER) {
+              queue.push([nextRow, nextCol]);
+              grid[nextRow][nextCol] = distance;
+            }
+
+            if (grid[nextRow][nextCol] === ISLAND) {
+              return (distance + 1) * -1;
+            }
+          }
+        }
+      }
+
+      distance -= 1;
+      currentQueue = queue;
+    }
+
+    return 1;
+  };
+
+  const isValidCoords = (row, col) =>
+    row >= 0 && row < rows && col >= 0 && col < cols;
+
+  for (let r = 0; r < rows; r++) {
+    for (let c = 0; c < cols; c++) {
+      if (grid[r][c] === WATER) continue;
+
+      exploreIslandDFS(r, c);
+      return connectIslandBFS();
+    }
+  }
+
+  return -1; // Error
+};