zigzag_conversion.cpp

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

#include<bits/stdc++.h>
class Solution {
public:
    string convert(string s, int numRows) {
        if(numRows <= 1) return s;
        string *A = new string[numRows];
        int n = s.size();
        int row = 0;
        int step = 1;
        for(int i = 0; i < n; i++){
            A[row].push_back(s[i]);
            if(row == 0) step = 1;
            else if(row == numRows - 1) step = -1;
            
            row = row + step;
        }
        string ans = "";
        for(int i = 0; i < numRows; i++){
            ans += A[i];
        }
        return ans;
    }
};