MEDIUM/src/medium/WordSearch.java

Author: fishercoder1534

MEDIUM/src/medium/WordSearch.java

@@ -0,0 +1,61 @@
+package medium;
+
+public class WordSearch {
+//I made it this time, completely by myself! Cheers! This let me completely understand backtracking!
+    public boolean exist(char[][] board, String word) {
+        int m = board.length, n = board[0].length;
+        for(int i = 0; i < m; i++){
+            for(int j = 0; j < n; j++){
+                boolean[][] visited = new boolean[m][n];
+                if(dfs(board, visited, i, j, word, 0)) return true;
+            }
+        }
+        return false;
+    }
+    
+    final int[] dirs = new int[]{0,1,0,-1,0};
+    
+    boolean dfs(char[][] board, boolean[][] visited, int row, int col, String word, int index){
+        if(index >= word.length() || word.charAt(index) != board[row][col]) return false;
+        else if(index == word.length()-1 && word.charAt(index) == board[row][col]) {
+            visited[row][col] = true;
+            return true;
+        }
+        visited[row][col] = true;//set it to true for this case
+        boolean result = false;
+        for(int i = 0; i < 4; i++){
+            int nextRow = row+dirs[i];
+            int nextCol = col+dirs[i+1];
+            if(nextRow < 0 || nextRow >= board.length || nextCol < 0 || nextCol >= board[0].length || visited[nextRow][nextCol]) continue;
+            result = dfs(board, visited, nextRow, nextCol, word, index+1);
+            if(result) return result;
+            else visited[nextRow][nextCol] = false;//set it back to false if this road doesn't work to allow it for other paths, this is backtracking!!!
+        }
+        return result;
+    }
+
+    public static void main(String...strings){
+        WordSearch test = new WordSearch();
+//        char[][] board = new char[][]{
+//                {'A','B','C','E'},
+//                {'S','F','C','S'},
+//                {'A','D','E','E'},
+//        };
+//        String word = "ABCCED";
+//        String word = "SEE";
+//        String word = "ABCD";
+        
+//        char[][] board = new char[][]{
+//                {'a','a'},
+//        };
+//        String word = "aaa";
+        
+        char[][] board = new char[][]{
+                {'A','B','C','E'},
+                {'S','F','E','S'},
+                {'A','D','E','E'},
+        };
+        String word = "ABCEFSADEESE";
+        System.out.println(test.exist(board, word));
+    }
+}