LeetCode 6 ZigZag Conversion（规律）

题目来源：https://leetcode.com/problems/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".

解题思路：

Zigzag:即循环对角线结构（

0				8				16
1			7	9			15	17
2		6		10		14		18
3	5			11	13			19
4				12				20

）

给出代码：

class Solution {
public:
    string convert(string s, int nRows){
    if(nRows == 1) return s;
    string res[nRows];
    int i = 0, j, gap = nRows-2;
    while(i < s.size()){
        for(j = 0; i < s.size() && j < nRows; ++j) res[j] += s[i++];
        for(j = gap; i < s.size() && j > 0; --j) res[j] += s[i++];
    }
    string str = "";
    for(i = 0; i < nRows; ++i)
        str += res[i];
    return str;
    }
};