LeetCode 006 ZigZag Conversion

题目描述：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".

 

分析：

对于每一层垂直元素的坐标 ( i, j ) = ( j + 1) ∗ n + i；对于每两层垂直元素之间的插入元素（斜对角元素）， ( i, j ) = ( j + 1) ∗ n − i。

 

代码如下：

class Solution {

public:

    string convert(string s, int nRows) {

        

        if(nRows <= 1 || s.size() <= 1) return s;

        string result;

        

        for(int i = 0; i < nRows; i++){

            for(int j = 0, index = i; index < s.size(); j++, index = (2 * nRows - 2) * j + i){

                result.append(1, s[index]);

                if(i == 0 || i == nRows - 1) continue;

                if(index + (nRows - i - 1) * 2 < s.size())

                    result.append(1, s[index + (nRows - i - 1) * 2]);

            }

        }

        

        return result;

        

    }

};