ZigZag Conversion

Problem Statement - link #

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);

Examples #

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

Solutions #

class Solution {
public:
    string convert(string s, int numRows) {
        if(numRows == 1) return s;
        int sz = s.size();
        string res="";
        int len = 2*numRows - 2;
        for(int i=0; i<numRows; i++)
            for(int j=0; i+j < sz; j+= len){
                res+=s[i+j];
                if(i and i!=numRows-1 and j+len-i < sz)
                    res+=s[j+len-i];
            }
        return res;
    }
};