solve 79.word-search

Author: andavid

vscode/79.word-search.java

@@ -0,0 +1,63 @@
+/*
+ * @lc app=leetcode id=79 lang=java
+ *
+ * [79] Word Search
+ *
+ * https://leetcode.com/problems/word-search/description/
+ *
+ * algorithms
+ * Medium (32.15%)
+ * Likes:    2097
+ * Dislikes: 107
+ * Total Accepted:    317.7K
+ * Total Submissions: 988K
+ * Testcase Example:  '[["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]]\n"ABCCED"'
+ *
+ * Given a 2D board and a word, find if the word exists in the grid.
+ *
+ * The word can be constructed from letters of sequentially adjacent cell,
+ * where "adjacent" cells are those horizontally or vertically neighboring. The
+ * same letter cell may not be used more than once.
+ *
+ * Example:
+ *
+ *
+ * board =
+ * [
+ * ⁠ ['A','B','C','E'],
+ * ⁠ ['S','F','C','S'],
+ * ⁠ ['A','D','E','E']
+ * ]
+ *
+ * Given word = "ABCCED", return true.
+ * Given word = "SEE", return true.
+ * Given word = "ABCB", return false.
+ *
+ *
+ */
+class Solution {
+  public boolean exist(char[][] board, String word) {
+    for (int i = 0; i < board.length; i++) {
+      for (int j = 0; j < board[i].length; j++) {
+        if (exist(board, i, j, word, 0)) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  public boolean exist(char[][] board, int i, int j, String word, int pos) {
+    if (pos == word.length()) return true;
+    if (i < 0 || i > board.length - 1 || j < 0 || j > board[i].length - 1) return false;
+    if (board[i][j] != word.charAt(pos)) return false;
+    board[i][j] = '*';
+    boolean result = exist(board, i - 1, j, word, pos + 1)
+                  || exist(board, i + 1, j, word, pos + 1)
+                  || exist(board, i, j - 1, word, pos + 1)
+                  || exist(board, i, j + 1, word, pos + 1);
+    board[i][j] = word.charAt(pos);
+    return result;
+  }
+}
+