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`

Solution

``````class Solution(object):
def convert(self, s, numRows):
if numRows == 1:
return s
n = len(s)
cycle = 2*numRows - 2
strlist = []
for i in range(numRows):
for j in range(i, n, cycle):
strlist.append(s[j])
if i != numRows-1 and i != 0 and j+cycle-2*i < n:
strlist.append(s[j+cycle-2*i])
newstr = ''.join(strlist)
return newstr``````