LeetCode刷题（C++）——ZigZag Conversion（Medium）

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：之字形转换如下：

                                   


观察可以发现：竖着的每一列都有numRows个元素，斜着的有numRows-2个元素，于是我们可以把竖着的一列和斜着的一列看成是一个循环周期，按照从上到下在从左下角到右上角的顺序存储字符。设置一个string数组，行数为numRows。

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