Convert a string into zigzag mode

Background:

Original problem Source: https://leetcode.com/problems/zigzag-conversion/

is to convert a string in zigzag format and return it. For example, the string "Abcdefghijk"

After conversion (3 lines):

A E IBDFHJC G K

Then print by line: AEIBDFHJCGK

If you are converting by 4 rows:

A GB Fhce IKD J

Printed: AGBFHCEIKDJ

Ideas:

In fact, the problem is like finding a regular problem. When converting to 3 lines, we can be in 4 units (4 = (3-1) * *. That is equal to (line number-1) * *), divide the string (take Abcdefghijk as an example ):

ABCD EFGH IJK

Then the No. 0 line that is printed after the conversion is actually the No. 0 element of each array after the split: a E I. corresponding to the original string is the No. 0, 4th, 8th.

So the law is 0,4,8,... 4*n.

then the 2nd line (the last line) printed after the conversion: Each element after printing is: C G K. In fact, it is the second element of each array after the split (subscript starting from 0) . Corresponds to the original string is: 2, 2+4,2+4*2,.. 2+4*n.

As can be seen from the above, the first line and the last line of the law is (set the number of rows for I, starting from 0): I+4*n (n=0,1,2 ...)

Other lines:

Or the above example, the first line of output is: B D F H J. Each element is the 1th and 1 elements in the segmented array. Corresponds to the original string as:

1,4-1,4+1,4*2-1,4*2+1 ...

So the rule is (set I as the number of rows): 4*n+i,4*n-i.

Code:

My code is not easy to write, and time is about 110ms, and no less time for this friend's code (107MS), so recommend the friend's code:

Source Code Origin: Https://leetcode.com/discuss/11948/my-python-solution

class solution:    #  @return  a string    def  Convert (self, s, nrows):         if nrows == 1 :            return s         d = 2*nrows -2        l =  len (s)         R =  '          for i in range (0, nrows):             MD = 2*nRows - 2 - 2*i             t = i             while t < L:                 r += s[t]                 if i != 0 and i!= nRows-1 and t+MD <  L:                     R += s[t+MD]                 t += d        return r

Convert a string into zigzag mode