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107 lines
2.2 KiB
Markdown
107 lines
2.2 KiB
Markdown
# [6. ZigZag Conversion](https://leetcode.com/problems/zigzag-conversion/)
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## 题目
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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)
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```
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P A H N
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A P L S I I G
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Y I R
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```
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And then read line by line: `"PAHNAPLSIIGYIR"`
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Write the code that will take a string and make this conversion given a number of rows:
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```
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string convert(string s, int numRows);
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```
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**Example 1:**
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```
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Input: s = "PAYPALISHIRING", numRows = 3
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Output: "PAHNAPLSIIGYIR"
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```
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**Example 2:**
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```
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Input: s = "PAYPALISHIRING", numRows = 4
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Output: "PINALSIGYAHRPI"
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Explanation:
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P I N
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A L S I G
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Y A H R
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P I
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```
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**Example 3:**
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```
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Input: s = "A", numRows = 1
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Output: "A"
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```
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**Constraints:**
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- `1 <= s.length <= 1000`
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- `s` consists of English letters (lower-case and upper-case), `','` and `'.'`.
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- `1 <= numRows <= 1000`
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## 题目大意
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将一个给定字符串 `s` 根据给定的行数 `numRows` ，以从上往下、从左到右进行 Z 字形排列。
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比如输入字符串为 `"PAYPALISHIRING"` 行数为 3 时，排列如下：
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```go
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P A H N
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A P L S I I G
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Y I R
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```
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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：`"PAHNAPLSIIGYIR"`。
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请你实现这个将字符串进行指定行数变换的函数：
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```go
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string convert(string s, int numRows);
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```
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## 解题思路
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- 这一题没有什么算法思想，考察的是对程序控制的能力。用 2 个变量保存方向，当垂直输出的行数达到了规定的目标行数以后，需要从下往上转折到第一行，循环中控制好方向ji
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## 代码
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```go
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package leetcode
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func convert(s string, numRows int) string {
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matrix, down, up := make([][]byte, numRows, numRows), 0, numRows-2
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for i := 0; i != len(s); {
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if down != numRows {
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matrix[down] = append(matrix[down], byte(s[i]))
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down++
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i++
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} else if up > 0 {
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matrix[up] = append(matrix[up], byte(s[i]))
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up--
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i++
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} else {
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up = numRows - 2
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down = 0
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}
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}
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solution := make([]byte, 0, len(s))
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for _, row := range matrix {
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for _, item := range row {
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solution = append(solution, item)
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}
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}
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return string(solution)
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}
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``` |