练几道，继续过Hard题目 http://www.cnblogs.com/charlesblc/p/6384132.html 继续过Hard模式的题目吧。 #TitleEditorialAcceptanceDifficultyFrequency 。 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 466 Count The Repetitions 24.6% 题目挺好的，但是描述太复杂。思路还是蛮清晰的。