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6. Zigzag Conversion

Medium

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

Solution

function convert(s: string, numRows: number): string {
    if (numRows < 2) {
        return s
    }
    const width = numRows * 2 - 2
    let result: string = ''
    let i
    let j
    for (let row = 0; row < numRows; row++) {
        i = row
        j = width - 2 * row
        while (i < s.length) {
            if (j > 0) {
                result += s[i]
            }
            i += j
            j = width - j
        }
    }
    return result
}

export { convert }

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