update 79 java

leetcode_java/src/main/java/LeetCodeJava/BackTrack/WordSearch.java

@@ -2,67 +2,63 @@
 
 // https://leetcode.com/problems/word-search/
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
 
 public class WordSearch {
 
-//      // TODO : fix V0
-//      // V0
-//      // IDEA : DFS OR BACKTRACK
-//      private int len;
-//      private int wid;
-//      private char[][] board_;
-//
-//      public boolean exist(char[][] board, String word) {
-//
-//          if (board == null || board.length == 0){
-//              return false;
-//          }
-//
-//          len = board.length;
-//          wid = board[0].length;
-//          board_ = board;
-//
-//          for (int y = 0; y < len; y++){
-//              for (int x = 0; x < wid; x++){
-//                  int index = 0;
-//                  if (this.backtrack_(x, y, word, index)){
-//                      return true;
-//                  }
-//              }
-//          }
-//
-//          return false;
-//      }
-//
-//    boolean backtrack_(int x, int y, String word, int index){
-//
-//          if (index >= word.length()){
-//            return true;
-//          }
-//
-//          if (x < 0 || x >= wid || y < 0 || y >= len || this.board_[y][x] != word.charAt(index)){
-//              return false;
-//          }
-//
-//          //public int[][] DIRECTIONS = new int[][]{{0, 1}, {1, 0}, {-1, 0}, {0, -1}};
-//          int[][] moves = new int[][]{ {0, 1}, {1, 0}, {-1, 0}, {0, -1} };
-//          for (int[] move : moves){
-//              index += 1;
-//              backtrack_(move[0], move[1], word, index);
-//              this.board[x][y] = word.charAt(index);
-//              index -= 1;
-//          }
-//          return false;
-//    }
+    // V0
+    // IDEA : DFS + BACKTRACK
+    public boolean exist(char[][] board, String word) {
+
+        int n = board.length;
+        int m = board[0].length;
+
+        /** NOTE !!! we define visited */
+        boolean[][] visited = new boolean[n][m];
+
+        for(int row = 0; row < n; row++){
+            for(int col = 0; col < m; col++){
+                if(board[row][col] == word.charAt(0)){
+                    if(dfs(row, col, word, 0, visited, board)){
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
 
+    public boolean dfs(int row, int col, String word, int lvl, boolean[][] visited, char[][] board){
+
+        int n = board.length;
+        int m = board[0].length;
+
+        if(lvl == word.length()){
+            return true;
+        }
+
+        if(row < 0 || row >= n || col < 0 || col >= m || visited[row][col] || board[row][col] != word.charAt(lvl)){
+            return false;
+        }
+
+        /** NOTE !!! mark cur x, y as visited */
+        visited[row][col] = true;
+        if ( dfs(row + 1, col, word, lvl + 1, visited, board) ||
+             dfs(row - 1, col, word, lvl + 1, visited, board) ||
+             dfs(row, col + 1, word, lvl + 1, visited, board) ||
+             dfs(row, col - 1, word, lvl + 1, visited, board) ){
+            return true;
+        }
+
+        /** NOTE !!! Backtrack : undo cur x, y as visited */
+        visited[row][col] = false;  // Backtrack
+
+        return false;
+    }
 
     // V1
     // IDEA : DFS + BACKTRACK
     // https://leetcode.com/problems/word-search/solutions/4791515/java-easy-solution-dfs-backtracking/
-    public boolean exist(char[][] board, String word) {
+    public boolean exist2(char[][] board, String word) {
         int n = board.length;
         int m = board[0].length;
 
@@ -71,7 +67,7 @@ public boolean exist(char[][] board, String word) {
         for(int row = 0; row < n; row++){
             for(int col = 0; col < m; col++){
                 if(board[row][col] == word.charAt(0)){
-                    if(dfs(row, col, word, 0, visited, board)){
+                    if(dfs2(row, col, word, 0, visited, board)){
                         return true;
                     }
                 }
@@ -80,7 +76,7 @@ public boolean exist(char[][] board, String word) {
         return false;
     }
 
-    public boolean dfs(int row, int col, String word, int lvl, boolean[][] visited, char[][] board){
+    public boolean dfs2(int row, int col, String word, int lvl, boolean[][] visited, char[][] board){
         int n = board.length;
         int m = board[0].length;
 
@@ -95,10 +91,10 @@ public boolean dfs(int row, int col, String word, int lvl, boolean[][] visited,
         visited[row][col] = true;
 
         boolean didFindNextCharacter =
-                dfs(row + 1, col, word, lvl + 1, visited, board) ||
-                dfs(row - 1, col, word, lvl + 1, visited, board) ||
-                dfs(row, col + 1, word, lvl + 1, visited, board) ||
-                dfs(row, col - 1, word, lvl + 1, visited, board);
+                dfs2(row + 1, col, word, lvl + 1, visited, board) ||
+                dfs2(row - 1, col, word, lvl + 1, visited, board) ||
+                dfs2(row, col + 1, word, lvl + 1, visited, board) ||
+                dfs2(row, col - 1, word, lvl + 1, visited, board);
 
         visited[row][col] = false;  // Backtrack
         return didFindNextCharacter;

leetcode_java/src/main/java/LeetCodeJava/BackTrack/WordSearch2.java

@@ -0,0 +1,14 @@
+package LeetCodeJava.BackTrack;
+
+// https://leetcode.com/problems/word-search-ii/description/?envType=list&envId=xoqag3yj
+
+import java.util.List;
+
+public class WordSearch2 {
+
+    // V0
+    public List<String> findWords(char[][] board, String[] words) {
+        return null;
+    }
+
+}