二刷79

docs/0079-word-search.adoc

@@ -23,10 +23,37 @@ Given word = "*SEE*", return *true*.
 Given word = "*ABCB*", return *false*.
 ----
 
+== 思路分析
+
+image:images/0079-01.png[{image_attr}]
+
+image:images/0079-02.png[{image_attr}]
 
 [[src-0079]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0079_WordSearch.java[tag=answer]
 ----
+--
+
+二刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0079_WordSearch_2.java[tag=answer]
+----
+--
+====
+
+== 参考资料
+
+. https://leetcode.cn/problems/word-search/solutions/2361646/79-dan-ci-sou-suo-hui-su-qing-xi-tu-jie-5yui2/?envType=study-plan-v2&envId=selected-coding-interview[79. 单词搜索 - 回溯，清晰图解^]
+
+
 

logbook/202406.adoc

@@ -841,13 +841,18 @@
 |{counter:codes}
 |{leetcode_base_url}/rotate-string/[796. Rotate String^]
 |{doc_base_url}/0796-rotate-string.adoc[题解]
-|✅
+|✅ 简单用 `contains`；复杂用 KMP 算法。
 
 |{counter:codes}
 |{leetcode_base_url}/course-schedule/[207. Course Schedule^]
 |{doc_base_url}/0207-course-schedule.adoc[题解]
 |✅ 拓扑排序
 
+|{counter:codes}
+|{leetcode_base_url}/word-search/[79. Word Search^]
+|{doc_base_url}/0079-word-search.adoc[题解]
+|✅ 回溯
+
 |===
 
 截止目前，本轮练习一共完成 {codes} 道题。

src/main/java/com/diguage/algo/leetcode/_0079_WordSearch.java

@@ -30,14 +30,17 @@
  * @since 2020-01-03 17:31
  */
 public class _0079_WordSearch {
-  // tag::answer[]
+    // tag::answer[]
 
     /**
      * Runtime: 4 ms, faster than 89.90% of Java online submissions for Word Search.
      *
      * Memory Usage: 38.4 MB, less than 97.96% of Java online submissions for Word Search.
      *
      * Copy from: https://leetcode.com/problems/word-search/discuss/27658/Accepted-very-short-Java-solution.-No-additional-space.[Accepted very short Java solution. No additional space. - LeetCode Discuss]
+     *
+     * @author D瓜哥 · https://www.diguage.com
+     * @since 2020-01-03 17:31
      */
     public boolean exist(char[][] board, String word) {
         if (Objects.isNull(board) || board.length == 0) {
@@ -76,7 +79,7 @@ private boolean exist(char[][] board, int y, int x, char[] word, int i) {
         return existable;
     }
 
-  // end::answer[]
+    // end::answer[]
 
 
     public static void main(String[] args) {

src/main/java/com/diguage/algo/leetcode/_0079_WordSearch_2.java

@@ -0,0 +1,62 @@
+package com.diguage.algo.leetcode;
+
+public class _0079_WordSearch_2 {
+  // tag::answer[]
+
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2024-09-21 21:39:49
+   */
+  public boolean exist(char[][] board, String word) {
+    for (int r = 0; r < board.length; r++) {
+      for (int c = 0; c < board[r].length; c++) {
+        if (board[r][c] == word.charAt(0)) {
+          if (backtrack(board, r, c, word, 0)) {
+            return true;
+          }
+        }
+      }
+    }
+    return false;
+  }
+
+  private boolean backtrack(char[][] board, int row, int column,
+                            String word, int idx) {
+    if (idx >= word.length()) {
+      return true;
+    }
+    if (row < 0 || row >= board.length
+      || column < 0 || column >= board[row].length
+      || board[row][column] == ' '
+      || board[row][column] != word.charAt(idx)) {
+      return false;
+    }
+    board[row][column] = ' ';
+    boolean result = backtrack(board, row - 1, column, word, idx + 1)
+      || backtrack(board, row + 1, column, word, idx + 1)
+      || backtrack(board, row, column - 1, word, idx + 1)
+      || backtrack(board, row, column + 1, word, idx + 1);
+    board[row][column] = word.charAt(idx);
+    return result;
+  }
+  // end::answer[]
+
+  public static void main(String[] args) {
+    _0079_WordSearch_2 solution = new _0079_WordSearch_2();
+    char[][] board = {
+      {'A', 'B', 'C', 'E'},
+      {'S', 'F', 'C', 'S'},
+      {'A', 'D', 'E', 'E'}};
+    String w1 = "ABCCED";
+    boolean r1 = solution.exist(board, w1);
+    System.out.println((r1) + " : " + r1);
+
+    String w2 = "SEE";
+    boolean r2 = solution.exist(board, w2);
+    System.out.println((r2) + " : " + r2);
+
+    String w3 = "ABCB";
+    boolean r3 = solution.exist(board, w3);
+    System.out.println((!r3) + " : " + r3);
+  }
+}