学习(Swift)Leetcode 6. ZigZag Conversion

Posted 2021-04-27 小冰溜

题目: 

https://leetcode.com/problems/zigzag-conversion/

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

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分析: 

这是一个关于String/模拟的Medium难度题

• 模拟题我感觉比较容易想解题思路，就是暴力着来就行。最直接的想法是简单粗暴，直接有几个row就创建几个数组，然后把对应的字母放到相应的数组中，最后一个数组一个数组的遍历，生成最后的结果。
  

• [本题实际的解法]模拟题也可以把具体过程画出来，然后看看有没有什么规律可循，没准这个规律很简单，这样写代码写起来也会很简单，出现bug的风险也会降低

具体思路图：

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代码:

class Solution { func convert(_ s: String, _ numRows: Int) -> String { if numRows == 1 { return s } let maxInterval = 2 * (numRows - 1) var chars = [Character]() for index in 0 ..< numRows { var loops = 0 while index + maxInterval * loops < s.count { let tempIndex1 = index + maxInterval * loops chars.append(Array(s)[tempIndex1]) if index == 0 || index == numRows - 1 { loops += 1 continue } let tempIndex2 = index + maxInterval * loops + maxInterval - (index * 2) if tempIndex2 < s.count { chars.append(Array(s)[tempIndex2]) } loops += 1 } } return String(chars) }}

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学到:

模拟题最主要是整理清晰流程，最好在白板上画一下，这样让面试官也比较清晰。

模拟题主要是考察编程能力，需要注意各种edge case，写完之后提出一些test case