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Xiaobian to share with you how leetcode to solve the zigzag transformation problem, I hope you have something to gain after reading this article, let's discuss it together!

Title Link

https://leetcode-cn.com/problems/zigzag-conversion/

Title Description

Zigzag a given string from top to bottom and from left to right according to the number of rows.

For example, when the input string is "LEETCODEISHIRING" and the number of rows is 3, the arrangement is as follows:

L C I R

E T O E S I I G

E D H N

After that, your output needs to be read line by line from left to right, producing a new string, such as: "LCIRETOESIIGEDHN."

Please implement this function that transforms a string into a specified number of rows:

string convert(string s, int numRows);

Example 1:

Input: s = "LEETCODEISHIRING", numRows = 3

Output: "LCIRETOESIIGEDHN"

Example 2:

Input: s = "LEETCODEISHIRING", numRows = 4

Output: "LDREOEIIECIHNTSG"

Explanation:

L D R

E O E I I

E C I H N

T S G

solution train of thought

Tag: string

The overall idea is to traverse the string, and in the traversal process, each line is regarded as a new string to form a string array, and finally the array can be spliced together.

If numRows=1, then the current string is the result, return directly

Otherwise, the whole string needs to go through a loop of down to right, down to right, and so on. Set the down variable to indicate whether it is down, and the loc variable to indicate the index of the current string array.

If down is true, loc+=1, string array subscripts move backward, adding the current character to the current string

If down is false, it means right, loc-=1, string array subscript moves forward, adds current character to current string

Time complexity: O(n), n is the length of string s

code

Java version

class Solution {

public String convert(String s, int numRows) {

if(numRows == 1)

return s;

int len = Math.min(s.length(), numRows);

String []rows = new String[len];

for(int i = 0; i< len; i++) rows[i] = "";

int loc = 0;

boolean down = false;

for(int i=0;i

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