Practice/Oracle/Leetcode 6. Zigzag Conversion

Leetcode 6. Zigzag Conversion

CodingMust

Problem

Given a string and a number of rows, arrange the characters in a wave (zigzag) pattern that flows vertically down and diagonally up, then read the characters row by row from left to right to produce a transformed string.

The wave pattern works as follows: characters are placed vertically downward until reaching the bottom row, then diagonally upward until reaching the top row, and this pattern repeats.

For example, with the string "HELLO" and 3 rows:

• The pattern looks like:

  H O E L L L

• Reading row by row: "HO" + "ELL" + "L" = "HOELL"

Requirements

1. Transform the input string according to the wave pattern across the specified number of rows
2. Return the characters read sequentially from the first row to the last row
3. Handle edge cases where numRows is 1 or exceeds the string length
4. Maintain the original character order within each row

Constraints

• 1 ≤ s.length ≤ 1000
• 1 ≤ numRows ≤ 1000
• s consists of English letters (uppercase and lowercase), digits, and symbols

Examples

Example 1:

Input: s = "HELLOWORLD", numRows = 3 Output: "HOLELWRDLO" Explanation: H O R E L W L D L O Reading row by row: "HOR" + "ELWLD" + "LO" = "HORELWLDLO"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4 Output: "PINALSIGYAHRPI" Explanation: P I N A L S I G Y A H R P I Reading row by row gives: "PIN" + "ALSIG" + "YAHR" + "PI"

Example 3:

Input: s = "AB", numRows = 1 Output: "AB" Explanation: With only one row, no transformation occurs.