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6. Z 字形变换 ​

6. Z 字形变换

将一个给定字符串 s 根据给定的行数 numRows ，以从上往下、从左到右进行 Z 字形排列。

比如输入字符串为 "PAYPALISHIRING" 行数为 3 时，排列如下：

P   A   H   N
A P L S I I G
Y   I   R

之后，你的输出需要从左往右逐行读取，产生出一个新的字符串，比如："PAHNAPLSIIGYIR"。

请你实现这个将字符串进行指定行数变换的函数：

string convert(string s, int numRows);

示例 ​

示例 1 ​

输入：s = "PAYPALISHIRING", numRows = 3

输出："PAHNAPLSIIGYIR"

示例 2 ​

输入：s = "PAYPALISHIRING", numRows = 4

输出："PINALSIGYAHRPI"

示例 3 ​

输入：s = "A", numRows = 1

输出："A"

提示 ​

1 <= s.length <= 1000

s 由英文字母（小写和大写）、',' 和 '.' 组成

1 <= numRows <= 1000

代码 ​

javascript
// 输入：s = "PAYPALISHIRING", numRows = 3
// 输出："PAHNAPLSIIGYIR"

export function convert(s, numRows) {
  if (numRows === 1 || numRows > s.length) return s
  const resObj = {}
  let rowIndex = 0
  let rowLine = 1
  for (let i = 0; i < s.length; i++) {
      resObj[String(rowIndex)] = resObj[String(rowIndex)] ? `${resObj[String(rowIndex)]}${s[i]}` : s[i]
      if (rowIndex === numRows - 1) rowLine = -1
      if (rowIndex === 0) rowLine = 1
      rowIndex = rowIndex + rowLine
  }
  let res = ''
  for (let i = 0; i < numRows; i++) {
      res = `${res}${resObj[String(i)]}`
  }
  return res
}
typescript
// 输入：s = "PAYPALISHIRING", numRows = 3
// 输出："PAHNAPLSIIGYIR"

export function convert(s: string, numRows: number): string {
  if (numRows === 1 || numRows > s.length) return s
  const resObj: { [key: string]: string } = {}
  let rowIndex = 0
  let rowLine = 1
  for (let i = 0; i < s.length; i++) {
      resObj[String(rowIndex)] = resObj[String(rowIndex)] ? `${resObj[String(rowIndex)]}${s[i]}` : s[i]
      if (rowIndex === numRows - 1) rowLine = -1
      if (rowIndex === 0) rowLine = 1
      rowIndex = rowIndex + rowLine
  }
  let res = ''
  for (let i = 0; i < numRows; i++) {
      res = `${res}${resObj[String(i)]}`
  }
  return res
}

测试代码 ​

ts
import { expect, test } from 'vitest'
import { convert } from './typescript.ts'
import { convert as convertJs } from './javascript.js'

test(`PAYPALISHIRING`, () => {
  expect(convert('PAYPALISHIRING', 3)).toEqual('PAHNAPLSIIGYIR')
})

test(`PAYPALISHIRING`, () => {
  expect(convertJs('PAYPALISHIRING', 3)).toEqual('PAHNAPLSIIGYIR')
})