leetcode之ZigZag Conversion

题目：

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"

.
解答：

就是找规律，对第一行和最后一行进行特殊处理即可

class Solution {
public:
string convert(string s, int numRows) {
int len = s.length();
if(numRows == 1)
return s;
string res = "";
for(int i = 0;i < numRows; ++i)
{
int p = i;
bool choose = true;
if(i == numRows - 1)
choose = false;
while(p < len)
{
if(choose)
{
res += s[p];
p = p + (numRows - i - 1) * 2;
if(!(i == 0 || i == numRows - 1))
choose = !choose;
}
else
{
res += s[p];
p = p + i * 2;
if(!(i == 0 || i == numRows - 1))
choose = !choose;
}
}
}
return res;
}
};