題目描述

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

AC程式碼

public class Solution{
public String convert
 
(String s, int nRows) {
    char[] c = s.toCharArray();
    int len = c.length;
    StringBuffer[] sb = new StringBuffer[nRows];
    for (int i = 0; i < sb.length; i++) sb[i] = new StringBuffer();
    
    int i = 0;
    while (i < len) {
        for (int idx = 0; idx < nRows && i <
 
 len; idx++) // vertically down
            sb[idx].append(c[i++]);
        for (int idx = nRows-2; idx >= 1 && i < len; idx--) // obliquely up
            sb[idx].append(c[i++]);
    }
    for (int idx = 1; idx < sb.length; idx++)
        sb[0].append(sb[idx]);
    return sb[0].toString();
}
}