# 【LeetCode】 6. ZigZag Conversion

## Description
> 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:

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

## Solution

* 用一個flag記錄現在往下還是往上。
* 用一個count記錄現在要丟在哪一行，根據flag每次++或--。

### Code

class Solution {
public:
    string convert(string s, int numRows) {
        if(numRows==1)return s;
        string *v =new string[numRows];
        for(int i=0,flag=0,count=0;i<s.length();i++)
        {
            v[count].push_back(s[i]);
            
            if(flag==0)
            {                
                if(count==numRows-1)
                {
                    count--;
                    flag=1;
                }
                else
                    count++;
            }
            else
            {
                if(count==0)
                {
                    count++;
                    flag=0;
                }
                else
                    count--;
            }
        }
        string ans;
        for(int i=0;i<numRows;i++)
            ans+=v[i];
        return ans;
    }
};

###### tags: `LeetCode` `C++`