54. 螺旋矩阵

Author: w2xi

Diff for: README.md

@@ -32,6 +32,7 @@
 |35|[搜索插入位置](https://leetcode.cn/problems/search-insert-position/)|[JavaScript](./algorithms/search-insert-position.js)|Easy|
 |48|[旋转图像](https://leetcode.cn/problems/rotate-image/)|[JavaScript](./algorithms/rotate-image.js)|Medium|
 |49|[字母异位词分组](https://leetcode.cn/problems/group-anagrams/)|[JavaScript](./algorithms/group-anagrams.js)|Medium|
+|54|[螺旋矩阵](https://leetcode.cn/problems/spiral-matrix/)|[JavaScript](./algorithms/spiral-matrix.js)|Medium|
 |58|[最后一个单词的长度](https://leetcode.cn/problems/length-of-last-word/)|[JavaScript](./algorithms/length-of-last-word.js)|Easy|
 |59|[螺旋矩阵 II](https://leetcode.cn/problems/spiral-matrix-ii/)|[JavaScript](./algorithms/spiral-matrix-ii.js)|Medium|
 |53|[最大子数组和](https://leetcode.cn/problems/maximum-subarray/)|[JavaScript](./algorithms/maximum-subarray.js)|Easy|

Diff for: algorithms/spiral-matrix.js

@@ -0,0 +1,37 @@
+/**
+ * 54. 螺旋矩阵
+ * 参考: https://leetcode.cn/problems/spiral-matrix/solution/cxiang-xi-ti-jie-by-youlookdeliciousc-3/
+ * @param {number[][]} matrix
+ * @return {number[]}
+ */
+var spiralOrder = function (matrix) {
+  if (matrix.length === 0) return [];
+
+  // 赋值上下左右边界
+  let left = 0,
+    top = 0;
+  let right = matrix[0].length - 1;
+  let bottom = matrix.length - 1;
+  let result = [];
+
+  while (true) {
+    // 从左到右
+    for (let i = left; i <= right; i++) result.push(matrix[top][i]);
+    // 重新设定上边界. 若上边界大于下边界，则遍历完成，下同
+    if (++top > bottom) break;
+
+    // 从上到下
+    for (let i = top; i <= bottom; i++) result.push(matrix[i][right]);
+    if (--right < left) break;
+
+    // 从右到左
+    for (let i = right; i >= left; i--) result.push(matrix[bottom][i]);
+    if (--bottom < top) break;
+
+    // 从下到上
+    for (let i = bottom; i >= top; i--) result.push(matrix[i][left]);
+    if (++left > right) break;
+  }
+
+  return result;
+};