6. Zigzag Conversion

难度: Medium

题目描述

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

解题思路

代码实现

解决方案

java

class Solution {
    public String convert(String s, int numRows) {
          if (numRows == 1) return s;
            StringBuilder sb = new StringBuilder();
        for (int i = 0; i < numRows; i++) {

            int j = i;
            while (j < s.length()) {
                if (i == 0 || i == numRows - 1) {
                    sb.append(s.charAt(j));
                    //System.out.print(s.charAt(j));
                    j = j + 2 * (numRows - 1);
                } else {
                    sb.append(s.charAt(j));
                    // System.out.print(s.charAt(j));
                    j = j + 2 * (numRows - 1);
                    if (j - 2 * i < s.length()) {
                        sb.append(s.charAt(j - 2 * i));
                        //System.out.print(s.charAt(j - 2 * (i)));
                    }


                }
            }


        }

        //System.out.println(sb.toString());
        return sb.toString();
    }
}