戈壁堂

link on JianShu

栈stack
144. Binary Tree Preorder Traversal Medium

Given a binary tree, return the preorder traversal of its nodes’ values.

link on JianShu

栈stack
145. Binary Tree Postorder Traversal Hard

Given a binary tree, return the postorder traversal of its nodes’ values.

link on JianShu

栈stack
844. Backspace String Compare Easy

Given two strings S and T, return if they are equal when both are typed into empty text editors. # means a backspace character.

link on JianShu

栈stack
94. Binary Tree Inorder Traversal Medium

Given a binary tree, return the inorder traversal of its nodes’ values.

link on JianShu

栈stack

valid parentheses

Given a string containing just the characters ‘(’, ‘)’, ‘{’, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.