LeetCode-in-All

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

func convert(s string, numRows int) string {
	topJump := (numRows-2)*2 + 2
	if topJump <= 0 {
		return s
	}
	size := len(s)
	resultArray := make([]byte, size)
	j := 0
	for i := 0; i < size; i += topJump {
		resultArray[j] = s[i]
		j++
	}
	for row := 1; row < numRows-1; row++ {
		for i := 0; i-row < size; i += topJump {
			iLeft := i - row
			iRight := i + row
			if iLeft > 0 {
				resultArray[j] = s[iLeft]
				j++
			}
			if iRight < size {
				resultArray[j] = s[iRight]
				j++
			}
		}
	}
	for i := topJump - numRows + 1; i < size; i += topJump {
		resultArray[j] = s[i]
		j++
	}
	return string(resultArray)
}

This site is open source. Improve this page.