Java版：ZigZag Conversion

2019-09-29

LeetCode 6. ZigZag Conversion

https://leetcode-cn.com/problems/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)

1
2
3

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:

1	string convert(string s, int numRows);

输入样例:

Example 1:

1 2	Input: s = "PAYPALISHIRING", numRows = 3 Output: "PAHNAPLSIIGYIR"

Example 2:

1 2	Input: -123 Output: -321

Example 3:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:

P     I    N
A   L S  I G
Y A   H R
P     I

Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

该题已提供代码：

class Solution {
    public String convert(String s, int numRows) {
        
    }
}

解题思路

实现代码

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

LeetCode测试结果

结语

至此，ZigZag Conversion 解决完毕！

Colin