俩娃大妈在职刷题

22. Generate Parentheses
看了最佳解法。明天再看其它解法。
Runtime: 1 ms, faster than 95.93% of Java online submissions for Generate Parentheses.
Memory Usage: 35.5 MB, less than 100.00% of Java online submissions for Generate Parentheses.

24. Swap Nodes in Pairs
Recurring, time O(n), space O(1)? Runtime: 0 ms, faster than 100.00% of Java online submissions for Swap Nodes in Pairs.
Memory Usage: 33.3 MB, less than 100.00% of Java online submissions for Swap Nodes in Pairs.

补充内容 (2019-5-14 10:05):
又是oncall。刷题都气若游丝了

补充内容 (2019-5-14 10:08):
Easy 101, medium 18

位运算
191. Number of 1 Bits
Time Complexity O(1), Space O(1)

补充内容 (2019-7-19 22:58):
190. Reverse Bits Time Complexity O(1), Space O(1)

补充内容 (2019-7-20 05:12):
136. Single Number

补充内容 (2019-7-20 11:23):
693. Binary Number with Alternating Bits  Time O(1), Space O(1)

suhehe 发表于 2019-7-19 22:33
位运算
191. Number of 1 Bits
Time Complexity O(1), Space O(1)

137. Single Number II

补充内容 (2019-7-23 02:35):
Time O(n), Space O(1). 小印Go code视频

260. Single Number III
傻瓜算法，map，Time O(n), Space O(n). Runtime: 6 ms, faster than 15.03% of Java online submissions for Single Number III.
Memory Usage: 38.8 MB, less than 98.00% of Java online submissions for Single Number III.


补充内容 (2019-7-23 23:13):
位运算， 笔记哥讲面试算法题。Time O(n), Space O(1). Runtime: 1 ms, faster than 99.77% of Java online submissions for Single Number III.
Memory Usage: 38.6 MB, less than 98.25% of Java online submis...

169. Majority Element
6种解法，Boyer-Moore Voting Algorithm 最惊艳 Time O(n), Space O(1)

229. Majority Element II
傻瓜HashMap 法， Time O(n), Space O(n). Runtime: 11 ms, faster than 17.79% of Java online submissions for Majority Element II.
Memory Usage: 40.4 MB, less than 96.55% of Java online submissions for Majority Element II.

补充内容 (2019-7-26 23:53):
进阶算法就是Boyer-Moore Voting Algorithm，Time O(n), Space O(1). 隐含条件是出现个数多于n/3 的数字小于或等于2.

补充内容 (2019-7-27 03:41):
对于出现个数多于array 长度 的 k 分之一，写出generalized Boyer-Moore Voting Algorithm, Time O(n*k), Space O(k).

258. Add Digits
while loop or recursion, Time complexity O(log N), Space complexity O(1)
Use math: a * 10^k % 9 = a (because of 10^k % 9 = 1), we can do Time O(1) and Space O(1).
1085. Sum of Digits in the Minimum Number
跟上题的不一样的地方是，只要一个while loop。首先用O(n) 求 min，在求sumOfdigits. Time O(n) and Space O(1).

859. Buddy Strings
Easy 我的老天啊！这道题折腾了3小时！还是用最naive的方法解, 一个一个数diff，Time O(n), Space O(n).

补充内容 (2019-8-1 04:54):
405. Convert a Number to Hexadecimal
mod = (num & 15); 不能用 mod = num % 16，因为这里有负数。

59. Spiral Matrix II
Time O(n^2), Space O(n^2)

补充内容 (2019-8-2 02:14):
54. Spiral Matrix
是Spiral Matrix II 的倒过来。Spiral Matrix II是 把matrix 赋值：result[row][col] = i; Spiral Matrix是把result.add(matrix[row][col]). 注意move direction就可以。

补充内容 (2019-8-2 02:17):
Spiral Matrix II是n x n matrix,  Spiral Matrix 是 m x n matrix. 方向都是只有4个，但是directionIndex 对II而已只要一个就可以，对Spiral Matrix I 必须有两个dirRowIndex 和dirColIndex

补充内容 (2019-8-2 05:07):
Spiral Matrix II 和 Spiral Matrix 都是内卷，Spiral Matrix III 是外卷