继续过Hard题目

	#	Title	Editorial	Acceptance	Difficulty	Frequency
。	65	Valid Number		12.6%	Hard
。	126	Word Ladder II		13.6%	Hard
。	149	Max Points on a Line		15.6%	Hard
。	146	LRU Cache		16.0%	Hard
。	68	Text Justification		18.1%	Hard
。	460	LFU Cache		19.0%	Hard
。	44	Wildcard Matching		19.0%	Hard
。	308	Range Sum Query 2D - Mutable		19.8%	Hard
。	4	Median of Two Sorted Arrays		20.8%	Hard
。	420	Strong Password Checker		21.0%	Hard
。	273	Integer to English Words		21.1%	Hard
。	30	Substring with Concatenation of All Words		21.7%	Hard
。	440	K-th Smallest in Lexicographical Order		22.1%	Hard
。	140	Word Break II		22.2%	Hard
。	212	Word Search II		22.2%	Hard
。	269	Alien Dictionary		22.3%	Hard
。	174	Dungeon Game		22.9%	Hard
。	214	Shortest Palindrome		23.0%	Hard
。	446	Arithmetic Slices II - Subsequence		23.0%	Hard
。	32	Longest Valid Parentheses		23.1%	Hard
。	295	Find Median from Data Stream		23.3%	Hard
。	132	Palindrome Partitioning II		23.4%	Hard
。	10	Regular Expression Matching		23.6%	Hard
。	76	Minimum Window Substring		23.8%	Hard
。	188	Best Time to Buy and Sell Stock IV		23.8%	Hard
。	321	Create Maximum Number		23.9%	Hard
。	135	Candy		23.9%	Hard
。	335	Self Crossing		23.9%	Hard
。	97	Interleaving String		23.9%	Hard
。	391	Perfect Rectangle		24.2%	Hard
。	158	Read N Characters Given Read4 II - Call multiple times		24.4%	Hard
。	466	Count The Repetitions		24.6%	Hard
。	336	Palindrome Pairs		24.7%	Hard
。	41	First Missing Positive		24.9%	Hard
。	124	Binary Tree Maximum Path Sum		25.0%	Hard
。	224	Basic Calculator		25.5%	Hard
。	218	The Skyline Problem		25.5%	Hard
。	84	Largest Rectangle in Histogram		25.6%	Hard
	23	Merge k Sorted Lists		25.9%	Hard
	45	Jump Game II		26.0%	Hard
	85	Maximal Rectangle		26.1%	Hard
	57	Insert Interval		26.3%	Hard
	138	Copy List with Random Pointer		26.6%	Hard
	233	Number of Digit One		27.3%	Hard
	381	Insert Delete GetRandom O(1) - Duplicates allowed		28.0%	Hard
	37	Sudoku Solver		28.1%	Hard
	432	All O`one Data Structure		28.2%	Hard
	87	Scramble String		28.3%	Hard
	123	Best Time to Buy and Sell Stock III		28.3%	Hard
	56	Merge Intervals		28.4%	Hard
	282	Expression Add Operators		28.5%	Hard
	316	Remove Duplicate Letters		28.6%	Hard
	164	Maximum Gap		28.6%	Hard
	99	Recover Binary Search Tree		28.7%	Hard
	327	Count of Range Sum		28.9%	Hard
	51	N-Queens		29.0%	Hard
	25	Reverse Nodes in k-Group		29.7%	Hard
	472	Concatenated Words		30.1%	Hard
	465	Optimal Account Balancing		30.1%	Hard
	248	Strobogrammatic Number III		30.5%	Hard
	72	Edit Distance		30.6%	Hard
	115	Distinct Subsequences		30.6%	Hard
	403	Frog Jump		30.9%	Hard
	411	Minimum Unique Word Abbreviation		31.1%	Hard
	239	Sliding Window Maximum		31.4%	Hard
	330	Patching Array		31.5%	Hard
	297	Serialize and Deserialize Binary Tree		31.6%	Hard
	354	Russian Doll Envelopes		31.8%	Hard
	358	Rearrange String k Distance Apart		31.8%	Hard
	33	Search in Rotated Sorted Array		31.9%	Hard
	363	Max Sum of Rectangle No Larger Than K		32.1%	Hard
	410	Split Array Largest Sum		32.2%	Hard
	480	Sliding Window Median		33.1%	Hard
	317	Shortest Distance from All Buildings		33.3%	Hard
	117	Populating Next Right Pointers in Each Node II		33.5%	Hard
	315	Count of Smaller Numbers After Self		33.5%	Hard
	301	Remove Invalid Parentheses		34.5%	Hard
	42	Trapping Rain Water		35.3%	Hard
	128	Longest Consecutive Sequence		35.3%	Hard
	329	Longest Increasing Path in a Matrix		35.4%	Hard
	407	Trapping Rain Water II		35.6%	Hard
	154	Find Minimum in Rotated Sorted Array II		36.2%	Hard
	265	Paint House II		37.1%	Hard
	272	Closest Binary Search Tree Value II		37.6%	Hard
	291	Word Pattern II		37.7%	Hard
	305	Number of Islands II		38.1%	Hard
	380	Insert Delete GetRandom O(1)		38.4%	Hard
	145	Binary Tree Postorder Traversal		38.4%	Hard
	340	Longest Substring with At Most K Distinct Characters		38.6%	Hard
	352	Data Stream as Disjoint Intervals		38.9%	Hard
	159	Longest Substring with At Most Two Distinct Characters		39.7%	Hard
	312	Burst Balloons		41.6%	Hard
	287	Find the Duplicate Number		41.8%	Hard
	425	Word Squares		41.9%	Hard
	52	N-Queens II		42.8%	Hard
	302	Smallest Rectangle Enclosing Black Pixels		44.0%	Hard
	471	Encode String with Shortest Length		44.2%	Hard
	296	Best Meeting Point		50.4%	Hard

218

The Skyline Problem

25.5%

Hard

解法很好，很厉害：

https://discuss.leetcode.com/topic/22482/short-java-solution 

84

Largest Rectangle in Histogram

25.6%

Hard

解法真的是太好了：

https://discuss.leetcode.com/topic/3913/my-concise-c-solution-ac-90-ms