word search

Author: zgpeace

code/LeetCode/src/backtracking/WordSearch.java

@@ -0,0 +1,65 @@
+package backtracking;
+
+// https://leetcode.com/problems/word-search/
+public class WordSearch {
+
+  public static void main(String[] args) {
+    WordSearch obj = new WordSearch();
+    char[][] board = {{'A','B','C','E'},
+                      {'S','F','C','S'},
+                      {'A','D','E','E'}};
+    //String word = "ABCCED";
+    //String word = "SEE";
+    String word = "ABCB";
+    boolean result = obj.exist(board, word);
+    System.out.println("result > " + result);
+  }
+
+  public boolean exist(char[][] board, String word) {
+    // check edge
+    if (word == null || word.length() == 0) {
+      return true;
+    }
+    if (board == null || board.length == 0 || board[0].length == 0) {
+      return false;
+    }
+    // used boolean
+    boolean[][] used = new boolean[board.length][board[0].length];
+
+    // dfs
+    for (int row = 0; row < board.length; row++) {
+      for (int col = 0; col < board[row].length; col++) {
+        if (dfs(board, word, used, row, col, 0)) {
+          return true;
+        }
+      }
+    }
+
+
+    return false;
+  }
+
+  private boolean dfs(char[][] board, String word, boolean[][] used, int row, int col, int wordIndex) {
+    if (word == null || wordIndex == word.length()) {
+      return true;
+    }
+    char currentChar = word.charAt(wordIndex);
+    if (row < 0 || col < 0
+        || row >= board.length || col >= board[row].length
+        || currentChar != board[row][col] || used[row][col])
+    {
+      return false;
+    }
+    // mark use
+    used[row][col] = true;
+    boolean result = dfs(board, word, used, row + 1, col, wordIndex + 1)
+        || dfs(board, word, used, row - 1, col, wordIndex + 1)
+        || dfs(board, word, used, row, col + 1, wordIndex + 1)
+        || dfs(board, word, used, row, col - 1, wordIndex + 1);
+
+    // mark not use
+    used[row][col] = false;
+
+    return result;
+  }
+}