LeetCode 6. ZigZag Conversion

"PAYPALISHIRING"

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 text, int nRows);

convert("PAYPALISHIRING", 3) should return "PAHNAPLSIIGYIR".

answer:

class Solution {
public:
    string convert(string s, int numRows) {
        string* blacket = new string[numRows * 2];
        string result = "";
        int index = 0;
        bool flag = false;
        if(numRows == 1)
            return s;
        for(int i = 0; i < s.length(); i ++){
            if(!flag && (index < numRows)){
                blacket[index ++] += s[i];
            }
            else if(index == numRows){
                index -= 2;
                flag = true;
            }
            if(flag){
                if(index > 0){
                    blacket[index --] += s[i];
                }
                else{
                    blacket[index ++] += s[i];
                    flag = false;
                } 
            }
        }
        for(int i = 0; i < numRows * 2; i ++){
            result += blacket[i];
        }
        delete[] blacket;
        return result;
    }
};