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Tested Python solution for LeetCode 6 with 20 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 6 # by problem number
lcpy gen -s zigzag_conversion # by problem name
"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
"PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a number of rows:
string convert(string s, int numRows);
Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"
Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P I N
A L S I G
Y A H R
P I
Input: s = "A", numRows = 1
Output: "A"
1 <= s.length <= 1000s consists of English letters (lower-case and upper-case), ',' and '.'.1 <= numRows <= 1000class Solution:
# Time: O(n)
# Space: O(n)
def convert(self, s: str, num_rows: int) -> str:
if num_rows == 1 or num_rows >= len(s):
return s
rows: list[list[str]] = [[] for _ in range(num_rows)]
current_row = 0
step = 1
for char in s:
rows[current_row].append(char)
if current_row == 0:
step = 1
elif current_row == num_rows - 1:
step = -1
current_row += step
return "".join("".join(row) for row in rows)
| Time | Space |
|---|---|
| O(n) | O(n) |