Island Perimeter

Author: lessfish

Algorithms/Island Perimeter/island-perimeter.js

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+// Source : https://leetcode.com/problems/island-perimeter/
+// Author : Han Zichi
+// Date   : 2016-11-20
+
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+var islandPerimeter = function(grid) {
+  if (grid.length === 0)
+    return 0;
+
+  let n = grid.length
+    , m = grid[0].length
+    , ans = 0;
+
+  const dir = [[1, 0], [-1, 0], [0, 1], [0, -1]];
+
+  for (let i = 0; i < n; i++)
+    for (let j = 0; j < m; j++) {
+      if (!grid[i][j])
+        continue;
+
+      for (let l = 0; l < 4; l++) {
+        let neighbourCellX = i + dir[l][0];
+        let neighbourCellY = j + dir[l][1];
+
+        if (neighbourCellX < 0 || neighbourCellX >= n
+            || neighbourCellY < 0 || neighbourCellY >= m) {
+          ans += 1;
+          continue;
+        }
+
+        ans += !grid[neighbourCellX][neighbourCellY];
+      }
+    }
+
+  return ans;
+};