ZigZag Conversion

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   NA P L S I I GY   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".

class Solution {public:    string convert(string s, int numRows) {    if(numRows<=1||s.size()<=1) return s;    string res;    for(int i=0;i<numRows;i++){    if(i==0||i==numRows-1){    for(int c =i;c<s.length();c+=2*numRows-2){    res += s[c];    }    }else{    bool cg = true;    for(int c=i;c<s.length();){    res +=s[c];    if(cg){    c += 2*(numRows-i-1);    }else{    c += 2*i;    }    cg =!cg;    }    }    }    return res;    }};