ARTS 033
Algorihm
6. ZigZag Conversion
Difficulty: Medium
The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
P A H N
A P L S I I G
Y I R
And then read line by line: "PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a number of rows:
string convert(string s, int numRows);
Example 1:
Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"
Example 2:
Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P I N
A L S I G
Y A H R
P I
Solution
我觉得这道题考察的就是找规律，你找到规律了就能解决了。
Language: Swift
class Solution{
func convert(_ s: String, _ numRows: Int) -> String {
if s.count <= numRows || numRows == 1{
return s;
}
var rowStrs = Array(repeating: "", count: numRows)
var step = 0
var start = 0
for i in 0..<s.count {
let char = s[s.index(s.startIndex, offsetBy: i)]
rowStrs[start].append(char)
if start == 0 {
step = 1;
}
else if start == (numRows - 1) {
step = -1;
}
start = start + step
}
var result = ""
for i in 0..<rowStrs.count {
result = result + rowStrs[i]
}
return result
}
}
7. Reverse Integer
Difficulty: Easy
Given a 32-bit signed integer, reverse digits of an integer.
Example 1:
Input: 123
Output: 321
Example 2:
Input: -123
Output: -321
Example 3:
Input: 120
Output: 21
Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
Solution
Language: Swift
class Solution {
func reverse(_ x: Int) -> Int {
var result = 0
var tem = x
while tem != 0 {
if result > Int32.max/10 || result < Int32.min / 10 {
return 0
}
result = result * 10 + tem % 10
tem = tem / 10
}
return result;
}
}
或者
class Solution {
func reverse(_ x: Int) -> Int {
var result = 0
var tem = x
while tem != 0 {
result = result * 10 + tem % 10
tem = tem / 10
if result > Int32.max || result < Int32.min {
return 0
}
}
return result;
}
}
Review
这篇文章讲的是Pure-singleton设计模式和Semi-singleton设计模式：
https://dandan2009.github.io/2019/10/24/design-patterns-by-tutorials-the-power-of-OOP-part-2/
Tips
talbeView cell上有视图正在动画，这时如果调用reloadData方法，动画会被打断，有没有方法被打断？ 目前还没找到方法
Share
这两天把Mac系统升级到了10.15，xcode升级到了xcode11.1，但是遇到了一些问题，在电脑不联网的情况模拟器不能安装APP或假死，然后Charles不联网的情况下会启动很慢，如果你的电脑是开发主力，建议谨慎升级。不知道是我的环境问题还是新系统问题。
-
Previous
Design patterns by Tutorials— The power of OOP (part 2) -
Next
Design patterns by Tutorials— The power of OOP (part 3)
