Zigzag Conversion

Problem 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);

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”

Constrains:

• 1 <= s.length <= 1000
• s consists of English letters (lower-case and upper-case), ',' and '.'.
• 1 <= numRows <= 1000

#include <vector>
#include <string>

using namespace std;

class Solution {
public:
    string convert(string s, int numRows) {
        // If numRows is 1 or less than or equal to the length of s, return s as is
        if (numRows == 1 || numRows >= s.length()) {
            return s;
        }

        // Initialize an array of strings to store characters for each row
        vector<string> rows(min(numRows, int(s.length())));
        int curRow = 0;
        bool goingDown = false;

        // Iterate through each character in the string and append it to the appropriate row
        for (char c : s) {
            rows[curRow] += c;
            // Change direction when reaching the first or the last row
            if (curRow == 0 || curRow == numRows - 1) goingDown = !goingDown;
            curRow += goingDown ? 1 : -1;
        }

        // Combine characters from all rows into a single string
        string ret;
        for (string row : rows) ret += row;

        return ret;
    }
};