add: wordSearch solution

Author: Cyjin-jani

word-search/Cyjin-jani.js

@@ -0,0 +1,41 @@
+//! dfs 구현 중에 막혀서 ai의 도움을 받아 풀이를 완성했습니다..
+var exist = function (board, word) {
+  const dx = [0, 0, -1, 1];
+  const dy = [-1, 1, 0, 0];
+
+  for (let i = 0; i < board.length; i++) {
+    for (let j = 0; j < board[i].length; j++) {
+      if (board[i][j] === word[0]) {
+        if (dfs(j, i, 0)) return true;
+      }
+    }
+  }
+
+  function dfs(x, y, index) {
+    // 성공
+    if (index === word.length) return true;
+
+    // 실패
+    if (x < 0 || y < 0 || y >= board.length || x >= board[y].length) return false;
+    if (board[y][x] === '#') return false;
+    if (board[y][x] !== word[index]) return false;
+
+    // 방문 표시
+    const origin = board[y][x];
+    board[y][x] = '#';
+
+    // 탐색
+    for (let i = 0; i < 4; i++) {
+      const newDy = y + dy[i];
+      const newDx = x + dx[i];
+
+      if (dfs(newDx, newDy, index + 1)) return true;
+    }
+    // 복원
+    board[y][x] = origin;
+
+    return false;
+  }
+
+  return false;
+};