word-search solution

Author: hyeri0903

word-search/hyeri0903.java

@@ -0,0 +1,40 @@
+class Solution {
+    public boolean exist(char[][] board, String word) {
+        /**
+        - backtracking (DFS)
+        - board[i][j] == word[0] 부터 start
+        - 상하좌우 탐색, 같은 칸 중복 탐색 x
+        - 틀리면 backtracking
+
+         */
+
+        for(int i = 0; i< board.length; i++) {
+            for(int j = 0; j< board[i].length; j++) {
+                if(dfs(i, j, 0, board, word)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    boolean dfs(int i, int j, int index, char[][] board, String word) {
+        //모두 다 찾은 경우
+        if(index == word.length()) return true;
+
+        //out of bound check
+        if(i < 0 || j < 0 || i >= board.length || j>= board[i].length || board[i][j] != word.charAt(index)) return false;
+
+        //방문처리
+        char cur = board[i][j];
+        board[i][j] = '#';
+
+        //4방향 탐색
+        boolean found = dfs(i+1, j, index+1, board, word) || dfs(i-1, j, index+1, board, word) || dfs(i, j+1, index+1, board, word) || dfs(i, j-1, index+1, board, word);
+
+        //backtracking
+        board[i][j] = cur;
+
+        return found;
+    }
+}