LeetCode*6. ZigZag Conversion

LeetCode题目链接

题目：

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)

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".

答案：

class Solution {
public:
    string convert(string s, int numRows) {
        if (numRows == 1) return s;
        string s_cp = s;
        int p = 2 * (numRows - 1);
        int k = 0;
        
        for (int i = 0; i < numRows && k < s.size(); i++) {
            for (int j = i; j < s.size(); j = j + p) {
                s[k++] = s_cp[j];
                int j2 = p - 2 * i + j;
                if (i && i != numRows-1 && j2 < s.size()) {
                    s[k++] = s_cp[j2];
                }
            }
        }
        
        return s;
    }
};

解析：

找规律。
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
==>
0 8 16 / 1 7 9 15 17 / 2 6 10 14 18 / 3 5 11 13 19 / 4 12 20