Leetcode Round 3 记录

[完全没有思路]

Array

1. Remove Duplicates from Sorted Array II

 

Tree

1. Symmetric Tree (No Recursion Solution: two queues)

2. Unique Binary Search Trees II

 

HashTable 

1. Sudoku Solver

 

Math

1. Divide Two Integers [实现除法，不能用乘除和取余符号； 位运算，二分]

2. Different Ways to Add Parentheses [分治法]

3. Number of Digit One [分情况枚举]

4. Excel Sheet Column Title [对Z分情况]

 

String

1. Decode Ways []

2. Shortest Palindrome []

3. Regular Expression Matching [特殊情况为第二个字符为"*"]

4. Distinct Subsuquences [dp]

 

DP

1. Gas Station []

 

Backtracking

1. Permutations II

 

 

[找不到正确的解法]

Array

1. Largest Retangle in Histogram

 

Tree

1. Binary Tree Maximum Path [递归helper函数]

 

String

1. Compare Version Numbers [设计比较方法是难点，test case]

2. Interleaving String [dp]

 

DataStructure

1. LRU [双向链表+节点操作]

 

DFS & BFS

1. Surrounded Regions [dfs栈溢出，需要用bfs，题目的精髓为dfs转bfs]

 

[有正确的解法但是复杂度不符合要求]

Array

1. Minimum Size Subarray Sum [Two Pointers]

2. Jump Game II [Greedy]

 

HashTable

1. Count Primes [素数生成法]

2. Repeated DNA Seq [HashSet不存字符串，存编码值]

 

String

1. Multiply Strings [有更加简洁的方法]

 

Math

1. Factorial Trailing Zeros [log复杂度]

 

[提交多次才通过]

Array

1. Set Matrix zeros [常数空间复杂度]

2. Spiral Matrix [边界cyc]

3. Kth Largest Element in an Array [partition函数应该使得数组保持从大到小的顺序]

 

String

1. Minimum Window Substring [two pointers, 移动的条件，两张HashMap]

2. Count and Say [设计字符串变化规则]

3. Atoi [bad case: +-2, +00012abc]

4. Multiply Strings [注意"9133"*"0", 结果为"0000"]

5. Longest Valid Parentheses ["((()))())"]

6. Shortest Palindrome [中心拓展法，先判断单点中心的拓展]

 

Tree

1. Populating Next Right Pointers II [两次贪心]

 

Math

1. Pow(x, n) [注意n为负数的边界条件]

2. Palindrome Number [while(x / base >= 10), x = (x % 10) / 10].