feat: 岛屿周长

Author: sl1673495

算法/DFS问题/岛屿的周长-463.js

@@ -0,0 +1,68 @@
+// https://leetcode-cn.com/problems/island-perimeter
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+var islandPerimeter = function (grid) {
+  let yLen = grid.length;
+  if (!yLen) return 0;
+  let xLen = grid[0].length;
+
+  let perimeter = { value: 0 };
+
+  for (let y = 0; y < yLen; y++) {
+    for (let x = 0; x < xLen; x++) {
+      if (grid[y][x] === 1) {
+        dfs(grid, y, x, perimeter);
+        break;
+      }
+    }
+  }
+
+  return perimeter.value;
+};
+
+function dfs(grid, y, x, perimeter) {
+  let cell = grid[y][x];
+  if (cell === "COMPLETE") return;
+
+  grid[y][x] = "COMPLETE";
+
+  let below = grid[y - 1] && grid[y - 1][x];
+  let upper = grid[y + 1] && grid[y + 1][x];
+  let left = grid[y][x - 1];
+  let right = grid[y][x + 1];
+
+  if (below) {
+    dfs(grid, y - 1, x, perimeter);
+  } else {
+    perimeter.value++;
+  }
+
+  if (upper) {
+    dfs(grid, y + 1, x, perimeter);
+  } else {
+    perimeter.value++;
+  }
+
+  if (left) {
+    dfs(grid, y, x - 1, perimeter);
+  } else {
+    perimeter.value++;
+  }
+
+  if (right) {
+    dfs(grid, y, x + 1, perimeter);
+  } else {
+    perimeter.value++;
+  }
+}
+
+console.log(
+  islandPerimeter([
+    [0, 1, 0, 0],
+    [1, 1, 1, 0],
+    [0, 1, 0, 0],
+    [1, 1, 0, 0],
+  ])
+);