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[leetcode] problem 6 – zigzag conversion

admin 11月 13, 2020 0

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 (string s, int numRows);

Example

No.1

Input: s = “PAYPALISHIRING”, numRows = 3

Output: “PAHNAPLSIIGYIR”

No.2

Input: s = “PAYPALISHIRING”, numRows = 4

Output: “PINALSIGYAHRPI”

Explanation:

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P     I    N
A   L S  I G
Y A   H R
P     I

Code

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public String (String s, int numRows) {
    if (numRows == 1)
        return s;
    
    StringBuffer result = new StringBuffer();
    int cycle = 2 * numRows - 2;

    for (int i = 0; i < numRows; i++) {
        for (int j = 0; i + j < s.length(); j += cycle) {
            result.append(s.charAt(i + j));

            if (i != 0 && i != numRows - 1 && cycle - i + j < s.length())
                result.append(s.charAt(cycle - i + j));
        }
    }

    return result.toString();
}
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