三刷54

Author: diguage

docs/0054-spiral-matrix.adoc

@@ -1,34 +1,34 @@
 [#0054-spiral-matrix]
-= 54. Spiral Matrix
+= 54. 螺旋矩阵
 
-{leetcode}/problems/spiral-matrix/[LeetCode - Spiral Matrix^]
+https://leetcode.cn/problems/spiral-matrix/[LeetCode - 54. 螺旋矩阵 ^]
 
-Given a matrix of _m_ x _n_ elements (_m_ rows, _n_ columns), return all elements of the matrix in spiral order.
+给你一个 `m` 行 `n` 列的矩阵 `matrix` ，请按照 *顺时针螺旋顺序*，返回矩阵中的所有元素。
 
-*Example 1:*
+*示例 1：*
 
-[subs="verbatim,quotes,macros"]
-----
-*Input:*
-[
- [ 1, 2, 3 ],
- [ 4, 5, 6 ],
- [ 7, 8, 9 ]
-]
-*Output:* [1,2,3,6,9,8,7,4,5]
-----
+image::images/0054-01.jpg[{image_attr}]
 
-*Example 2:*
-[subs="verbatim,quotes,macros"]
-----
-*Input:*
-[
-  [1, 2, 3, 4],
-  [5, 6, 7, 8],
-  [9,10,11,12]
-]
-*Output:* [1,2,3,4,8,12,11,10,9,5,6,7]
-----
+....
+输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
+输出：[1,2,3,6,9,8,7,4,5]
+....
+
+*示例 2：*
+
+image::images/0054-02.jpg[{image_attr}]
+
+....
+输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
+输出：[1,2,3,4,8,12,11,10,9,5,6,7]
+....
+
+*提示：*
+
+* `m == matrix.length`
+* `n == matrix[i].length`
+* `+1 <= m, n <= 10+`
+* `+-100 <= matrix[i][j] <= 100+`
 
 == 思路分析
 
@@ -56,6 +56,15 @@ include::{sourcedir}/_0054_SpiralMatrix.java[tag=answer]
 include::{sourcedir}/_0054_SpiralMatrix_2.java[tag=answer]
 ----
 --
+
+三刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0054_SpiralMatrix_3.java[tag=answer]
+----
+--
 ====
 
 == 参考资料

docs/images/0054-01.jpg

@@ -235,6 +235,11 @@ endif::[]
 |{doc_base_url}/0028-find-the-index-of-the-first-occurrence-in-a-string.adoc[题解]
 |✅ 暴力破解。更有的解法是 KMP 算法、Boyer-Moore 算法、Sunday 算法等算法。
 
+|{counter:codes2503}
+|{leetcode_base_url}/spiral-matrix/[54. Spiral Matrix^]
+|{doc_base_url}/0054-spiral-matrix.adoc[题解]
+|✅ 使用递归来推进层级。注意处理细节。另外，在“上”和“右”能覆盖“全部”（比如一行多列或者多行一列）时，才能在“下”之前根据长度返回。
+
 |===
 ˚
 截止目前，本轮练习一共完成 {codes2503} 道题。

docs/images/0054-02.jpg

@@ -0,0 +1,55 @@
+package com.diguage.algo.leetcode;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class _0054_SpiralMatrix_3 {
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-04-12 23:18:24
+   */
+  public List<Integer> spiralOrder(int[][] matrix) {
+    List<Integer> result = new ArrayList<>(matrix.length * matrix[0].length);
+    bfs(matrix, 0, 0, matrix.length - 1, matrix[0].length - 1, result);
+    return result;
+  }
+
+  private void bfs(int[][] matrix,
+                   int columnStart, int rowStart,
+                   int columnEnd, int rowEnd,
+                   List<Integer> result) {
+    if (columnStart > columnEnd || rowStart > rowEnd) {
+      return;
+    }
+    // 上
+    for (int i = rowStart; i <= rowEnd; i++) {
+      result.add(matrix[columnStart][i]);
+    }
+    // 右
+    for (int i = columnStart + 1; i <= columnEnd; i++) {
+      result.add(matrix[i][rowEnd]);
+    }
+    if (result.size() == matrix.length * matrix[0].length) {
+      return;
+    }
+    // 下
+    for (int i = rowEnd - 1; i >= rowStart; i--) {
+      result.add(matrix[columnEnd][i]);
+    }
+    // 左
+    for (int i = columnEnd - 1; i > columnStart; i--) {
+      result.add(matrix[i][rowStart]);
+    }
+    bfs(matrix, columnStart + 1, rowStart + 1,
+      columnEnd - 1, rowEnd - 1, result);
+  }
+  // end::answer[]
+
+  public static void main(String[] args) {
+    new _0054_SpiralMatrix_3().spiralOrder(new int[][]{
+      {1, 2, 3, 4},
+      {5, 6, 7, 8},
+      {9, 10, 11, 12},
+    });
+  }
+}