[Swift] 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

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

풀러가기

문제 이해

코드

class Solution {
  func convert(_ s: String, _ numRows: Int) -> String {
    if numRows == 1 {
      return s
    }
    var array = [[Character]](repeating: [Character](repeating: Character("-"), count: s.count), count: numRows)
    
    var j = 0
    var i = 0
    var isDown = true
    for c in s {
      if !isDown {
        i += 1
        j -= 1
      }
      array[j][i] = c
      
      if isDown {
        j += 1
      }
      
      if numRows == 2 && j == 2 {
        j = 0
        i += 1
        continue
      }
      
      if j == numRows {
        isDown = false
        j -= 1
      } else if j == 1 && !isDown {
        j = 0
        i += 1
        isDown = true
      }
    }
    
    var ret = ""
    
    for arr in array {
      for c in arr {
        let s = String(c)
        if s != "-" {
          ret += s
        }
      }
    }
    
    return ret
  }
}

풀이

-

다른 분의 멋진 코드

잘 배웠습니다.

-