ZigZag Conversion 回旋字符串

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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”.
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这道题是一个变换，只要找到其中的规律就很好做题。

假设结果存在一个string result中

原字符串存于s

经过观察我们可以发现
红色部分的变换为：

result.append(1,s[j*(numRows+numRows-2)+i])

绿色部分的变换为

result.append(1,s[(j+1)*(numRows+numRows-2)-i])

其中i是第i行，j是（红色或者绿）的第j个数

所以我们可以这么写代码：

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

            }

        }
        return result;


    }
};