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 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”.

思路：建立numRows个数组分别记录每一行的字符串，遍历一遍字符串，将每个字符放在对应的数组中，遍历的顺序是先向下，在对角线，之后以此重复，最后将每一行的代码拼接起来即可，代码如下：

class Solution {public:    string convert(string s, int numRows) {        if(numRows==1)            return s;        int len = s.length(),i = 0,j;        string *res = new string[numRows];        while(i < len){            for(j = 0; j < numRows && i < len; ++j)                res[j] += s[i++];            for(j = numRows - 2; j > 0 && i < len; j--)                res[j] += s[i++];        }        string ret = "";        for(i = 0; i < numRows; ++i)            ret +=res[i];        return ret;    }};