[LeetCode] ZigZag Conversion 解题报告

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"

.
» Solve this problem

[解题思路]
数学题。巨无聊的一道题，真正面试过程中，不大可能出这种问题。
n=4
P I N
A L S I G
Y A H R
P I

N=5
P H
A S I
Y I R
P L I G
A N

所以，对于每一层主元素(红色元素)的坐标 (i,j)= (j+1 )*n +i
对于每两个主元素之间的插入元素（绿色元素），(j+1)*n -i

[code]1:    string convert(string s, int nRows) {
2:      // Start typing your C/C++ solution below
3:      // DO NOT write int main() function
4:      if(nRows <= 1) return s;
5:      string result;
6:      if(s.size() ==0) return result;
7:      for(int i =0; i< nRows; i++)
8:      {
9:        for(int j =0, index =i; index < s.size();
10:            j++, index = (2*nRows-2)*j +i)
11:        {
12:          result.append(1, s[index]);  //red element
13:          if(i ==0 || i == nRows-1)   //green element
14:          {
15:            continue;
16:          }
17:          if(index+(nRows- i-1)*2 < s.size())
18:          {
19:            result.append(1, s[index+(nRows- i-1)*2]);
20:          }
21:        }
22:      }
23:      return result;
24:    }