Zigzag Conversion LeetCode Solution

Here, We see Zigzag Conversion problem Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc., with different approaches.

Zigzag Conversion LeetCode Solution

Problem Statement ->

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"

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"

• C++ Solution
• Java Solution
• JavaScript Solution
• Python Solution

Zigzag Conversion Leetcode Solution C++ ->

class Solution {
public:
    string convert(string s, int numRows) {

        if (numRows == 1) return s;

        string ret;
        int n = s.size();
        int cycleLen = 2 * numRows - 2;

        for (int i = 0; i < numRows; i++) {
            for (int j = 0; j + i < n; j += cycleLen) {
                ret += s[j + i];
                if (i != 0 && i != numRows - 1 && j + cycleLen - i < n)
                    ret += s[j + cycleLen - i];
            }
        }
        return ret;
    }
};
Code language: C++ (cpp)

Zigzag Conversion Leetcode Solution Java ->

class Solution {
    public String convert(String s, int numRows) {

        if (numRows == 1) return s;

        StringBuilder ret = new StringBuilder();
        int n = s.length();
        int cycleLen = 2 * numRows - 2;

        for (int i = 0; i < numRows; i++) {
            for (int j = 0; j + i < n; j += cycleLen) {
                ret.append(s.charAt(j + i));
                if (i != 0 && i != numRows - 1 && j + cycleLen - i < n)
                    ret.append(s.charAt(j + cycleLen - i));
            }
        }
        return ret.toString();
    }
}
Code language: Java (java)

Zigzag Conversion Leetcode Solution JavaScript ->

var convert = function(s, numRows) {
    // return original string if can't zigzag
    if (numRows === 1 || s.length < numRows) return s;

    let rows = []
    let converted = '';
    let reverse = false;
    let count = 0

    // prepare rows
    for (let i = 0; i < numRows; i++) rows[i] = [];
    // reverse the push flow when reaching turning points
    for (let i = 0; i < s.length; i++) {
        rows[count].push(s[i]);
        reverse ? count-- : count++;
        if (count === numRows - 1 || count === 0) reverse = !reverse;
    }
    // put together converted string
    return rows.reduce((converted, cur) => converted + cur.join(''), '');
};
Code language: JavaScript (javascript)

Zigzag Conversion Leetcode Solution Python ->

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        if numRows == 1:
            return s
            
        row_arr = [""] * numRows
        row_idx = 1
        going_up = True

        for ch in s:
            row_arr[row_idx-1] += ch
            if row_idx == numRows:
                going_up = False
            elif row_idx == 1:
                going_up = True
            
            if going_up:
                row_idx += 1
            else:
                row_idx -= 1
        
        return "".join(row_arr)
Code language: Python (python)