|
| 1 | +## Z 字形变换 |
| 2 | +### 题目描述 |
| 3 | + |
| 4 | +将一个给定字符串根据给定的行数,以从上往下、从左到右进行 Z 字形排列。 |
| 5 | + |
| 6 | +比如输入字符串为 `"LEETCODEISHIRING"` 行数为 3 时,排列如下: |
| 7 | + |
| 8 | +``` |
| 9 | +L C I R |
| 10 | +E T O E S I I G |
| 11 | +E D H N |
| 12 | +``` |
| 13 | + |
| 14 | +之后,你的输出需要从左往右逐行读取,产生出一个新的字符串,比如:`"LCIRETOESIIGEDHN"`。 |
| 15 | + |
| 16 | +请你实现这个将字符串进行指定行数变换的函数: |
| 17 | +``` |
| 18 | +string convert(string s, int numRows); |
| 19 | +``` |
| 20 | + |
| 21 | +**示例 1:** |
| 22 | +``` |
| 23 | +输入: s = "LEETCODEISHIRING", numRows = 3 |
| 24 | +输出: "LCIRETOESIIGEDHN" |
| 25 | +``` |
| 26 | + |
| 27 | +**示例 2:** |
| 28 | +``` |
| 29 | +输入: s = "LEETCODEISHIRING", numRows = 4 |
| 30 | +输出: "LDREOEIIECIHNTSG" |
| 31 | +解释: |
| 32 | + |
| 33 | +L D R |
| 34 | +E O E I I |
| 35 | +E C I H N |
| 36 | +T S G |
| 37 | +``` |
| 38 | + |
| 39 | +### 解法 |
| 40 | + |
| 41 | +```java |
| 42 | +class Solution { |
| 43 | + public String convert(String s, int numRows) { |
| 44 | + if (numRows == 1) return s; |
| 45 | + StringBuilder result = new StringBuilder(); |
| 46 | + int group = 2 * numRows - 2; |
| 47 | + for (int i = 1; i <= numRows; i++) { |
| 48 | + int interval = 2 * numRows - 2 * i; |
| 49 | + if (i == numRows) interval = 2 * numRows - 2; |
| 50 | + int index = i; |
| 51 | + while (index <= s.length()) { |
| 52 | + result.append(s.charAt(index - 1)); |
| 53 | + index += interval; |
| 54 | + interval = group - interval; |
| 55 | + if (interval == 0) interval = group; |
| 56 | + } |
| 57 | + } |
| 58 | + return result.toString(); |
| 59 | + } |
| 60 | +} |
| 61 | +``` |
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