[leetcode 6] ZigZag Conversion

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本文介绍了一种将字符串以Z字形方式排列并按行读取的算法实现。该算法适用于给定行数的情况，通过观察模式并利用数学规律进行编码。文章提供了C++代码示例，展示了如何实现这一字符串转换。

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：找到数学规律

class Solution {
public:
    string convert(string s, int nRows) {
        if (nRows <= 1 || s.size() < 2) {
            return s;
        }
        string res;
        for (int i = 0; i < nRows; i++) {
            for (int j = 0, index = i; index < s.size(); j++, index = (nRows*2 -2)*j+i) {
                res += s[index];
                if (i == 0 || i == nRows - 1) {
                    continue;
                }
                if (index + (nRows-i-1)*2 < s.size()) {
                    res += s[index + (nRows-i-1)*2];
                }
            }
        }
        return res;
        
    }
};