master BFS in algo Binary Tree ZigZag Level Order Traversal 103 Populating Next Right Pointers in Each Node 116 Populating Next Right Pointers in Each Node II 117 Binary Tree Right Side View 199 Number of Islands 200 Minesweeper 529 All Nodes Distance K in Binary Tree 863 Shortest Path in a Grid with Obstacles Eliminat Maximum Candies You Can Get from Boxes 1298 Binary Tree ZigZag Level Order Traversal 103

master BFS in algo Jump Game III 1306 Check if There is a Valid Path in a Grid 1391 Reorder Routes to Make All Paths Lead to the City Zero 1466 Map of Highest Peak 1765 Path With Minimum Effort 1631 Count Subtrees With Max Distance Between Cities 1617 Jump Game III 1306

master BST in algo 前序中序后序 N-ary Tree Level Order Traversal 429 Maximum Depth of Binary Tree 104 <strong>最浅距离的二叉树</strong> Count Complete Tree Nodes 222 Binary Tree Paths 257 Find Bottom Left Tree Value 513 Path Sum 112 Path Sum 113 Construct Binary Tree from Preorder and Inorder Traversal 105 Construct Binary Tree from Inorder and Postorder Traversal 106 insert 前序中序后序

Cyclic Sort，循环排序 Missing Number 268 Find the Duplicate Number 287 Find All Numbers Disappeared in an Array 448 Find All Duplicates in an Array 442 First Missing Positive 41 All Ancestors of a Node in a Directed Acyclic Graph 2192 可以用来处理数组中的数值限定在一定的区间的问题。这种模式一个个遍历数组中的元素，如果当前这个数它不在其应该在的位置的话，就把它和它应该在的那个位置上的数交换一下。

about Dynamic Programming learing note

my fast slow point leet code list leetcode Linked List Cycle 141 Linked List Cycle II 142 Happy Number 202 Reorder List 143 Remove Duplicates from Sorted Array 26 Find the Duplicate Number 287 Maximum Twin Sum of a Linked Li Delete the Middle Node of a Linked Lis Convert Sorted List to Binary Search Tree 109 Car Fleet II 1776 Linked List Cycle 141

有趣的图论 facebook 顺着你的 connection 找到你的小学同学就是图。

my Merge Intervalsleet code list leetcode Insert Interval 57 Employee Free Time 759 Merge Intervals 56 The Skyline Problem 218 Non-overlapping Intervals 435 Minimum Number of Arrows to Burst Balloons 452 My Calendar I 729 My Calendar II 731 My Calendar III 732 Describe the Painting 1943 Falling Squares 699 Task Scheduler 621 区间合并模式是一个用来处理有区间重叠的很高效的技术。在设计到区间的很多问题中，通常咱们需要要么判断是否有重叠，要么合并区间，如果他们重叠的话。这个模式是这么起作用的：

quick way to know Queue and Stack Implement Stack using Queues 225 这题其实要考虑这个系统是 read heave 还是 write heave， 影响后面你用 push O(n) 还是 pop O(n)的解法

reverse LinkedList pattern in algorithm, 反转套路