胜利不像山坡上的蒲公英一样 唾手可得

昨天加班的时候 看樊战胜张 真的感觉到紧张

题目描述

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

Example 3:

Input: s = "A", numRows = 1
Output: "A"

 

Constraints:

• 1 <= s.length <= 1000
• s consists of English letters (lower-case and upper-case), ',' and '.'.
• 1 <= numRows <= 1000

解题思路

可以声明一个二维数组 遍历s 声明一个标识 再合适的位置调头

function convert(s: string, numRows: number): string {
  let arr = [] as string[][]
  let i = 0
  let index = 0
  let len = s.length
  // 要标识index的状态 是++ 还是--
  let isIncrement = false
  while (i < len) {
    let str = s.charAt(i)
    if (arr[index] && Array.isArray(arr[index])) {
      ;(arr[index] as Array<string>).push(str)
    } else {
      arr[index] = [str]
    }
    if (index === 0 || index === numRows - 1) isIncrement = !isIncrement
    isIncrement ? index++ : index--
    i++
  }
  return arr.reduce((initValue, item) => initValue + item.join(""), "")
}

BayBay!!!!