LeetCode-in-All
6. Zigzag Conversion
Medium
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 <= 1000sconsists of English letters (lower-case and upper-case),','and'.'.1 <= numRows <= 1000
Solution
# @param {String} s
# @param {Integer} num_rows
# @return {String}
def convert(s, num_rows)
s_len = s.length
return s if num_rows == 1
max_dist = num_rows * 2 - 2
buf = ''
(0...num_rows).each do |i|
index = i
if i.zero? || i == num_rows - 1
while index < s_len
buf << s[index]
index += max_dist
end
else
while index < s_len
buf << s[index]
index += max_dist - i * 2
break if index >= s_len
buf << s[index]
index += i * 2
end
end
end
buf
end