[Leetcode] 144. Binary Tree Preorder Traversal {Day 10 Tree} (In Python)

코드들은 https://github.com/Eastar-DS/Python/tree/main/14%20Days%20Study%20Plan%20about%20Data_Structure에도 있습니다

오늘 푼 세문제덕에 preorder, inorder, postorder traversal을 공부했다.