Zigzag Conversion Problem


Description

LeetCode Problem 6.

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)

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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:

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string convert(string s, int numRows);

Example 1:

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Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

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Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P     I    N
A   L S  I G
Y A   H R
P     I

Example 3:

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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


Sample C++ Code

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string convert(string s, int nRows) {
    
    if (nRows <= 1)
        return s;

    const int len = (int)s.length();
    string *str = new string[nRows];

    int row = 0, step = 1;
    for (int i = 0; i < len; ++i)
    {
        str[row].push_back(s[i]);

        if (row == 0)
            step = 1;
        else if (row == nRows - 1)
            step = -1;

        row += step;
    }

    s.clear();
    for (int j = 0; j < nRows; ++j)
    {
        s.append(str[j]);
    }

    delete[] str;
    return s;
}




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