[ Leetcode ] 6. ZigZag Conversion - Java

 

 

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

 
 class Solution {
    public String convert(String s, int numRows) {
        if(s.length() == numRows){
            return s;
        }
        if(numRows == 1){
            return s;
        }
        String[] rowStr = new String[numRows];
        for(int i=0; i< numRows; i++){
            rowStr[i] = "";
        }
        String[] strs = s.split("");

        int rowNum = 0;
        boolean isPlus = true;
        for(String str : strs){
            rowStr[rowNum] += str;

            if(isPlus){
                rowNum++;
            }else{
                rowNum--;
            }
            if(rowNum == numRows-1) {
                isPlus = false;
            }
            if(rowNum == 0) {
                isPlus = true;
            }
        }
        String answer = "";
        for(String str : rowStr){
            answer += str;
        }
        return answer;
    }
 }