Solution: Zigzag Conversion

Problem Statement

Given a string s and a numRows integer representing the number of rows, write the string in a zigzag pattern on the given number of rows and then read it line by line, and return the resultant string.

The zigzag pattern means writing characters in a diagonal down-and-up fashion. For example, given the string "HELLOPROGRAMMING" and 4 rows, the pattern would look like:

H     R     M
E   P O   M I
L O   G A   N
L     R     G

Reading it line by line gives us "HRMEPOMILOGANLRG".

Examples

Example 1:

Input:

.....

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NITIN KUMAR

· 3 months ago

in the python solution the complexity is not O(n ) but O(n^2 ) , that's is because every time we do


# Append the character to the current row
            rows[currentRow] += c

it's taking O( n) time not O(1) , for python we should use list instead of string and then concatinate it at the end.

python solution:

class Solution:

    def create_zig_zag(self, s: str, rows : int) -> list[str]:
        res = [[]  for _ in range(rows)]
        i = 0 
        going_down = False
        for ch in s: 
            res[i].append(ch)

            if i == 0 or i == (rows - 1):
                going_down = not going_down
            
            i += 1 if going_down else -1
        
        return res

    def convert(self, s: str, rows: int) -> str:
        # ToDo: Wrte Your