leetcode problem 6 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".

简单的模拟题。

直接上代码：（Runtime: 26 ms）

class Solution {
public:
    string convert(string s, int nRows) {
        if (nRows == 1)
            return s;
        string res = s;
        int round = 2*nRows - 2;
        int len = res.length();
        int pos = 0;
        for (int i = 0; i < nRows; ++i) {
            int k = 0;
            int cur = k*round+i;

            while (true) {
                cur = k*round + i;
                if (cur >= len)
                    break;
                res[pos++] = s[cur];

                if (i != 0 && i != nRows - 1) {
                    cur = (k+1)*round - i;
                    if (cur >= len)
                        break;
                    res[pos++] = s[cur];
                }
                ++k;
            }
        }
        return res;
    }
};