20190306

Author: mJackie

Top100.md

@@ -1,11 +1,3 @@
-<img src="img/readme.png"></a>
-
-The user's favorite 100 problems are very classic. If you are a newbie, this is the best way to get started with leetcode.
-
----
-
-用户最喜欢的100道题都是很经典的问题，是新手入门 leetcode 的最好方式。
-
 ### Top 100 Liked Questions
 
 | \# | Problems | Difficulty | Solution |

TopInterview.md

@@ -8,131 +8,143 @@
 | 003  | [Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/) | Medium | [Java](./code/lc3.java)
 | 004  | [Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays) | Hard | [Java](./code/lc4.java)
 | 005  | [Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/) |Medium|[Java](./code/lc5.java)
-
+| 007  | [Reverse Integer](https://leetcode.com/problems/reverse-integer/) |Easy|[Java](./code/lc7.java)
+| 008  | [String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/) |Medium|[Java](./code/lc8.java)
 | 010  | [Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/) | Hard | [Java](./code/lc10.java)
 | 011  | [Container With Most Water](https://leetcode.com/problems/container-with-most-water/) |Medium| [Java](./code/lc11.java)
-
-
-| 015  | [3Sum](https://leetcode.com/problems/3sum/) |Medium| [Java](./code/lc15.java)
-| 017  | [Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) |Medium| [Java](./code/lc17.java)
+| 013  | [Roman to Integer](https://leetcode.com/problems/roman-to-integer) |Easy| [Java](./code/lc13.java)
+| 014  | [Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix) |Easy| [Java](./code/lc14.java)
+| 015  | [3Sum](https://leetcode.com/problems/3sum/) | Medium | [Java](./code/lc15.java)
+| 017  | [Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) | Medium | [Java](./code/lc17.java)
 | 019  | [Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/) | Easy | [Java](./code/lc19.java)
 | 020  | [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/) | Easy | [Java](./code/lc20.java)
 | 021  | [Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/) | Easy | [Java](./code/lc21.java)
 | 022  | [Generate Parentheses](https://leetcode.com/problems/generate-parentheses/) |Medium| [Java](./code/lc22.java)
 | 023  | [Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/) | Hard | [Java](./code/lc23.java)
-| 029  |
-
+| 026  | [Remove Duplicates from Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array) | Easy | [Java](./code/lc26.java)
+| 028  | [Implement strStr()](https://leetcode.com/problems/implement-strstr) | Easy | [Java](./code/lc28.java)
+| 029  | [Divide Two Integers](https://leetcode.com/problems/divide-two-integers) | Medium | [Java](./code/lc29.java)
 | 033  | [Search in Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/) |Medium| [Java](./code/lc33.java)
 | 034  | [Search for a Range](https://leetcode.com/problems/search-for-a-range/) |Medium| [Java](./code/lc34.java)
 | 035  | [Search Insert Position](https://leetcode.com/problems/search-insert-position/) |Medium| [Java](./code/lc35.java)
-| 036  |
-| 041  |
-
-
+| 036  | [Valid Sudoku]() | Medium | [Java](./code/lc36.java)
+| 038  | [Count and Say]() | Easy | [Java](./code/lc38.java)
+| 041  | [First Missing Positive]() | Hard | [Java](./code/lc41.java)
 | 042  | [Trapping Rain Water](https://leetcode.com/problems/trapping-rain-water/) | Hard | [Java](./code/lc42.java)
-| 044  |
-
+| 044  | [Wildcard Matching]() | Hard | [Java](./code/lc44.java)
 | 046  | [Permutations](https://leetcode.com/problems/permutations/)  |Medium| [Java](./code/lc46.java)
 | 048  | [Rotate Image](https://leetcode.com/problems/rotate-image/)  |Medium| [Java](./code/lc48.java)
 | 049  | [Group Anagrams](https://leetcode.com/problems/anagrams/)|Medium| [Java](./code/lc49.java)
-| 050  |
-
+| 050  | [Pow(x, n)]() | Medium | [Java](./code/lc50.java)
 | 053  | [Maximum Subarray](https://leetcode.com/problems/maximum-subarray/) |Medium| [Java](./code/lc53.java)
-| 054  |
+| 054  | [Spiral Matrix]() | Medium | [Java](./code/lc54.java)
 | 055  | [Jump Game](https://leetcode.com/problems/jump-game/)  |Medium| [Java](./code/lc55.java)
 | 056  | [Merge Intervals](https://leetcode.com/problems/merge-intervals/) |Medium| [Java](./code/lc56.java)
 | 062  | [Unique Paths](https://leetcode.com/problems/unique-paths/)  |Medium| [Java](./code/lc62.java)
-
-
+| 066  | [Plus One]() | Easy | [Java](./code/lc66.java)
+| 069  | [Sqrt(x)]() | Easy | [Java](./code/lc69.java)
 | 070  | [Climbing Stairs](https://leetcode.com/problems/climbing-stairs/) | Easy | [Java](./code/lc70.java)
-
-| 073  |
-
+| 073  | [Set Matrix Zeroes]() | Medium | [Java](./code/lc73.java)
 | 075  | [Sort Colors](https://leetcode.com/problems/sort-colors/)|Medium| [Java](./code/lc75.java)
 | 076  | [Minimum Window Substring](https://leetcode.com/problems/minimum-window-substring) | Hard| [Java](./code/lc76.java)
 | 078  | [Subsets](https://leetcode.com/problems/subsets/) |Medium| [Java](./code/lc78.java)
 | 079  | [Word Search](https://leetcode.com/problems/word-search/)|Medium| [Java](./code/lc79.java)
 | 084  | [Largest Rectangle in Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram) | Hard | [Java](./code/lc84.java)
-
-
+| 088  | [Merge Sorted Array]() | Easy | [Java](./code/lc88.java)
+| 091  | [Decode Ways]() | Medium | [Java](./code/lc91.java)
 | 094  | [Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/) |Medium| [Java](./code/lc94.java)
-
 | 098  | [Validate Binary Search Tree](https://leetcode.com/problems/validate-binary-search-tree/) |Medium| [Java](./code/lc98.java)
 | 101  | [Symmetric Tree](https://leetcode.com/problems/symmetric-tree/) | Easy | [Java](./code/lc101.java)
 | 102  | [Binary Tree Level Order Traversal](https://leetcode.com/problems/binary-tree-level-order-traversal/) | Easy | [Java](./code/lc102.java)
-
+| 103  | [Binary Tree Zigzag Level Order Traversal]() | Medium | [Java](./code/lc103.java)
 | 104  | [Maximum Depth of Binary Tree](https://leetcode.com/problems/maximum-depth-of-binary-tree/) | Easy | [Java](./code/lc104.java)
 | 105  | [Construct Binary Tree from Preorder and Inorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/) |Medium| [Java](./code/lc105.java)
-
-
-
-
+| 108  | [Convert Sorted Array to Binary Search Tree]() | Easy | [Java](./code/lc108.java)
+| 116  | [Populating Next Right Pointers in Each Node ]() | Medium | [Java](./code/lc116.java)
+| 118  | [Pascal's Triangle]() | Easy | [Java](./code/lc118.java)
 | 121  | [Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/) | Easy | [Java](./code/lc121.java)
-
+| 122  | [Best Time to Buy and Sell Stock II]() | Easy | [Java](./code/lc122].java)
 | 124  | [Binary Tree Maximum Path Sum](https://leetcode.com/problems/binary-tree-maximum-path-sum/) | Hard | [Java](./code/lc124.java)
-
-
+| 125  | [Valid Palindrome]() | Easy | [Java](./code/lc125.java)
+| 127  | [Word Ladder]() | Medium | [Java](./code/lc127.java)
 | 128  | [Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence/) | Hard | [Java](./code/lc128.java)
-
-
-
+| 130  | [Surrounded Regions]() | Medium | [Java](./code/lc130.java)
+| 131  | [Palindrome Partitioning]() | Medium | [Java](./code/lc131.java)
+| 134  | [Gas Station]() | Medium | [Java](./code/lc134.java)
 | 136  | [Single Number](https://leetcode.com/problems/single-number) | Easy | [Java](./code/lc136.java) 
-
+| 138  | [Copy List with Random Pointer]() | Medium | [Java](./code/lc138.java)
 | 139  | [Word Break](https://leetcode.com/problems/word-break/) |Medium| [Java](./code/lc139.java)
-
+| 140  | [Word Break II]() | Hard | [Java](./code/lc140.java)
 | 141  | [Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/) | Easy | [Java](./code/lc141.java)
-
 | 146  | [LRU Cache](https://leetcode.com/problems/lru-cache/)  | Hard | [Java](./code/lc146.java)
 | 148  | [Sort List](https://leetcode.com/problems/sort-list/)  |Medium| [Java](./code/lc148.java)
-
-
-
+| 149  | [Max Points on a Line]() | Hard | [Java](./code/lc149.java)
+| 150  | [Evaluate Reverse Polish Notation]() | Medium | [Java](./code/lc150.java)
 | 152  | [Maximum Product Subarray](https://leetcode.com/problems/maximum-product-subarray/) |Medium| [Java](./code/lc152.java)
 | 155  | [Min Stack](https://leetcode.com/problems/min-stack/)  | Easy | [Java](./code/lc155.java)
 | 160  | [Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/) | Easy | [Java](./code/lc160.java)
-
-
-
-
+| 162  | [Find Peak Element]() | Medium | [Java](./code/lc162.java)
+| 163  | [Missing Ranges](https://leetcode.com/problems/missing-ranges) | Medium | [没权限]
+| 166  | [Fraction to Recurring Decimal]() | Medium | [Java](./code/lc166.java)
 | 169  | [Majority Element](https://leetcode.com/problems/majority-element/) | Easy | [Java](./code/lc169.java)
+| 171  | [Excel Sheet Column Number]() | Easy | [Java](./code/lc171.java)
+| 172  | [Factorial Trailing Zeroes]() | Easy | [Java](./code/lc172.java)
+| 179  | [Largest Number]() | Medium | [Java](./code/lc179.java)
+| 189  | [Rotate Array]() | Easy | [Java](./code/lc189.java)
+| 190  | [Reverse Bits]() | Easy | [Java](./code/lc190.java)
+| 191  | [Number of 1 Bits]() | Easy | [Java](./code/lc191.java)
 | 198  | [House Robber](https://leetcode.com/problems/house-robber/)  | Easy | [Java](./code/lc198.java)
 | 200  | [Number of Islands](https://leetcode.com/problems/number-of-islands/) |Medium| [Java](./code/lc200.java)
-
-
+| 202  | [Happy Number]() | Easy | [Java](./code/lc202.java)
+| 204  | [Count Primes]() | Easy | [Java](./code/lc204.java)
 | 206  | [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/) | Easy |[Java](./code/lc206.java)
 | 207  | [Course Schedule](https://leetcode.com/problems/course-schedule/) |Medium|[Java](./code/lc207.java)
 | 208  | [Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/) |Medium| [Java](./code/lc208.java)
-
-
-
+| 210  | [Course Schedule II]() | Medium | [Java](./code/lc210.java)
+| 212  | [Word Search II]() | Hard | [Java](./code/lc212.java)
 | 215  | [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/) |Medium| [Java](./code/lc215.java)
-
-
-
+| 217  | [Contains Duplicate]() | Easy | [Java](./code/lc217.java)
+| 218  | [The Skyline Problem]() | Hard | [Java](./code/lc218.java)
+| 227  | [Basic Calculator II]() | Medium | [Java](./code/lc227.java)
+| 230  | [Kth Smallest Element in a BST]() | Medium | [Java](./code/lc230.java)
 | 234  | [Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list/) | Easy | [Java](./code/lc234.java)
 | 236  | [Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/) |Medium| [Java](./code/lc236.java)
-
+| 237  | [Delete Node in a Linked List]() |  | [Java](./code/lc237.java)
 | 238  | [Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/) |Medium| [Java](./code/lc238.java)
 | 239  | [Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/) | Hard | [Java](./code/lc239.java)
 | 240  | [Search a 2D Matrix II](https://leetcode.com/problems/search-a-2d-matrix-ii/) |Medium| [Java](./code/lc240.java)
-
-
+| 242  | [Valid Anagram]() |  | [Java](./code/lc242.java)
+| 251  | [Flatten 2D Vector](https://leetcode.com/problems/flatten-2d-vector) | Medium | [没权限]
+| 253  | [Meeting Rooms II](https://leetcode.com/problems/meeting-rooms-ii) | Medium | [没权限]
+| 268  | [Missing Number]() |  | [Java](./code/lc268.java)
+| 269  | [Alien Dictionary]() | Hard |[没权限]
+| 277  | [Find the Celebrity]() | Medium | [没权限]
 | 279  | [Perfect Squares](https://leetcode.com/problems/perfect-squares/) |Medium| [Java](./code/lc279.java)
 | 283  | [Move Zeroes](https://leetcode.com/problems/move-zeroes/)| Easy | [Java](./code/lc283.java)
-
+| 285  | [Inorder Successor in BST](https://leetcode.com/problems/inorder-successor-in-bst) | Medium | [没权限]
 | 287  | [Find the Duplicate Number](https://leetcode.com/problems/find-the-duplicate-number/) | Hard | [Java](./code/lc287.java)
-
-
+| 295  | [Find Median from Data Stream]() | Hard | [Java](./code/lc295.java)
 | 297  | [Serialize and Deserialize Binary Tree](https://leetcode.com/problems/serialize-and-deserialize-binary-tree/) | Hard | [Java](./code/lc297.java)
 | 300  | [Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/) |Medium| [Java](./code/lc300.java)
-
-
+| 308  | [Range Sum Query 2D - Mutable](https://leetcode.com/problems/range-sum-query-2d-mutable) | Medium | [没权限]
+| 315  | [Count of Smaller Numbers After Self]() | Hard | [Java](./code/lc315.java)
 | 322  | [Coin Change](https://leetcode.com/problems/coin-change/)|Medium| [Java](./code/lc322.java)
-
-
-
-
-
-
-| 337  | [House Robber III](https://leetcode.com/problems/house-robber-iii/) |Medium| [Java](./code/lc337.java)
+| 324  | [Wiggle Sort II]() | Medium | [Java](./code/lc324.java)
+| 326  | [Power of Three]() | Easy | [Java](./code/lc326.java)
+| 328  | [Odd Even Linked List]() | Medium | [Java](./code/lc328.java)
+| 329  | [Longest Increasing Path in a Matrix]() | Hard | [Java](./code/lc329.java)
+| 334  | [Increasing Triplet Subsequence]() | Medium | [Java](./code/lc334.java)
+| 340  | [Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters) | Hard | [Java](./code/lc340.java)
+| 341  | [Flatten Nested List Iterator]() | Medium | [Java](./code/lc341.java)
+| 344  | [Reverse String]() | Easy | [Java](./code/lc344.java)
 | 347  | [Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/) |Medium| [Java](./code/lc347.java)
+| 348  | [Design Tic-Tac-Toe](https://leetcode.com/problems/design-tic-tac-toe) | Medium | [没权限]
+| 350  | [Intersection of Two Arrays II]() | Easy | [Java](./code/lc350.java)
+| 371  | [Sum of Two Integers]() | Easy | [Java](./code/lc371.java)
+| 378  | [Kth Smallest Element in a Sorted Matrix]() | Medium | [Java](./code/lc378.java)
+| 380  | [Insert Delete GetRandom O(1)]() | Medium | [Java](./code/lc380.java)
+| 384  | [Shuffle an Array]() | Medium | [Java](./code/lc384.java)
+| 387  | [First Unique Character in a String]() | Easy | [Java](./code/lc387.java)
+| 395  | [Longest Substring with At Least K Repeating Characters]() | Medium | [Java](./code/lc395.java)
+| 412  | [Fizz Buzz](https://leetcode.com/problems/fizz-buzz) | Easy | [Java](./code/lc412.java)
+| 454  | [4Sum II](https://leetcode.com/problems/4sum-ii) | Medium | [Java](./code/lc454.java)

code/lc350.java

@@ -0,0 +1,32 @@
+package code;
+/*
+ * 350. Intersection of Two Arrays II
+ * 题意：求两个数组的交集
+ * 难度：Easy
+ * 分类：Hash Table, Two Pointers, Binary Search, Sort
+ * 思路：HashMap, 注意重复的数字，用计数进行处理
+ * Tips：如果两个数组足够大，那么如何处理？
+ *       如果其中一个可以加载到内存中，则HashMap处理以后，流式读取第二个数组
+ *       如果都不能加载，则先外部排序，再用类似归并链表的方式读取数据
+ */
+import java.util.ArrayList;
+import java.util.HashMap;
+
+public class lc350 {
+    public int[] intersect(int[] nums1, int[] nums2) {
+        ArrayList<Integer> res = new ArrayList();
+        HashMap<Integer, Integer> hm = new HashMap();
+        for (int i : nums1) hm.put(i, hm.getOrDefault(i, 0) + 1);
+        for (int i : nums2) {
+            if (hm.getOrDefault(i, 0) > 0) {
+                res.add(i);
+                hm.put(i, hm.get(i) - 1);
+            }
+        }
+        int[] res_arr = new int[res.size()];    //toArray方法只能转化为 Integer[] 类型，和返回值不一致
+        for (int i = 0; i < res_arr.length; i++) {
+            res_arr[i] = res.get(i);
+        }
+        return res_arr;
+    }
+}

code/lc371.java

@@ -0,0 +1,15 @@
+package code;
+/*
+ * 371. Sum of Two Integers
+ * 题意：两个数相加，但不能用 + - 操作符号
+ * 难度：Easy
+ * 分类：Bit Maniputation
+ * 思路：自己没想起来
+ *      https://leetcode.com/problems/sum-of-two-integers/discuss/84278/A-summary%3A-how-to-use-bit-manipulation-to-solve-problems-easily-and-efficiently
+ * Tips：
+ */
+public class lc371 {
+    public int getSum(int a, int b) {
+        return b==0? a:getSum(a^b, (a&b)<<1);   // a^b 为不算进位的结果，加上进位
+    }
+}

code/lc387.java

@@ -0,0 +1,20 @@
+package code;
+/*
+ * 387. First Unique Character in a String
+ * 题意：第一个没有重复的字符索引
+ * 难度：Easy
+ * 分类：Hash Table, String
+ * 思路：
+ * Tips：
+ */
+public class lc387 {
+    public int firstUniqChar(String s) {
+        int freq [] = new int[26];
+        for(int i = 0; i < s.length(); i ++)
+            freq [s.charAt(i) - 'a'] ++;
+        for(int i = 0; i < s.length(); i ++)
+            if(freq [s.charAt(i) - 'a'] == 1)
+                return i;
+        return -1;
+    }
+}

code/lc395.java

@@ -0,0 +1,54 @@
+package code;
+/*
+ * 395. Longest Substring with At Least K Repeating Characters
+ * 题意：求最长子串，子串中每个字符都必须最少出现K次
+ * 难度：Medium
+ * 分类：
+ * 思路：两种，一种是 Two Pointers 模板找子串，不过外层加了个循环，表示子串中有几个不同的字符
+ *      递归，每次统计字符出现了几次，不足K的作为分割点
+ * Tips：lc76模板
+ *       想到了利用不足K的分割点作为切点，挺难的
+ */
+public class lc395 {
+    public int longestSubstring(String s, int k) {
+        int res = 0;
+        for (int i = 1; i <= 26 ; i++) {
+            int left = 0, right = 0, cur_uni_char = 0, less_than_k_char = 0;
+            int[] map = new int[26];
+            while(right<s.length()){    //右边推进
+                map[s.charAt(right)-'a']++;
+                if(map[s.charAt(right)-'a']==k) less_than_k_char++;
+                if(map[s.charAt(right)-'a']==1) cur_uni_char++;
+                right++;
+
+                if( cur_uni_char==i && less_than_k_char==i) res = Math.max(res, right-left);
+
+                else if(cur_uni_char>i){    //左边推进
+                    while(cur_uni_char!=i){
+                        map[s.charAt(left)-'a']--;
+                        if(map[s.charAt(left)-'a']==0) cur_uni_char--;
+                        if((map[s.charAt(left)-'a']==k-1)) less_than_k_char--;
+                        left++;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+
+    public int longestSubstring2(String s, int k) {
+        return helper(s, k, 0, s.length()-1);
+    }
+    public int helper(String s, int k, int left, int right){
+        int[] map = new int[26];
+        for (int i = left; i <= right ; i++) map[s.charAt(i)-'a']++;
+        for (int i = left; i <= right ; i++) {  //遍历所有的分割点
+            if(map[s.charAt(i)-'a']<k){
+                int left_max = helper(s, k, left, i-1);
+                int right_max = helper(s, k, i+1, right);
+                return Math.max(left_max, right_max);   //直接返回了，就不遍历后续了，因为子情况会去计算后续的分割点
+            }
+        }
+        return right-left+1;
+    }
+}