dsa · medium

Zigzag Conversion

Write s in a zigzag across num_rows rows, going down then diagonally up, then down again. Read the characters row by row and return that concatenation.

Arguments

• s — the source string
• num_rows — how many rows the zigzag uses

Example

s = "PAYPALISHIRING", num_rows = 3 writes:

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

Reading rows: "PAHNAPLSIIGYIR".

Constraints

1 <= s.length <= 1000 1 <= num_rows <= 1000 Hidden tests include near-max size for this bound; a slower-than-intended solution TLEs.

Examples

Example 1

Input:
"PAYPALISHIRING"
3

Expected:
PAHNAPLSIIGYIR

Example 2

Input:
"PAYPALISHIRING"
4

Expected:
PINALSIGYAHRPI

Example 3

Input:
"A"
1

Expected:
A

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