Based on Solution

Kth Problem

• (378) Kth Smallest Element in a Sorted Matrix
• (Lintcode 465) Kth Smallest Sum in Two Sorted Arrays

Two Pointers of Same Direction

• (3) Longest Substring Without Repeating Characters
• (209) Minimum Size Subarray Sum
• (340) Longest Substring with At Most K Distinct Characters

Union Find

• (261) Graph Valid Tree
• (305) Number of Island II
• (Lintcode 590) Connecting Graph II
• (Lintcode 629) Minimum Spanning Tree
• (721) Accounts Merge

Trie

• (208) Implement Trie (Prefix Tree)
• (211) Add and Search Word - Data structure design
• (212) Word Search II

Prefix Sum

• (Lintcode 138) Subarray Sum
• (Lintcode 405) Submatrix Sum

Stack

• (155) Min Stack
• (394) Decode String
• (654) Maximum Binary Tree
• (Lintcode 22) Flatten List
• (Lintcode 402) Continuous Subarray Sum

Stack + Design

• (341) Flatten Nested List Iterator

Monotone Stack

• (42) Trapping Rain Water
• (84) Largest Rectangle in Histogram
• (85) Maximal Rectangle

Two Heaps - minHeap and maxHeap

• (295) Find Median from Data Stream
• (480) Sliding Window Median

Min Heap

• (407) Trapping Rain Water II

Sweep Line

• (253) Meeting Rooms II
• (Lintcode 391) Number of Airplanes in the Skyline

Binary Search

• (29) Divide Two Integers
• (69) Sqrt(x)
• (287) Find the Duplicate Number
• (644) Maximum Average Subarray II
• (Lintcode 183) Wood Cut
• (Lintcode 437) Copy Books
• (Lintcode 586) Sqrt(x) II

Deque

• (239) Sliding Window Maximum
• (346) Moving Average from Data Stream

Dynamic Programming

• (198) House Robber

DFS + Binary Tree