[LeetCode] 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".

找到间隔相邻的规律,O(n)的时间可以完成

 1 class Solution {
 2 private:
 3     int step[2];
 4 public:
 5     string convert(string s, int nRows) {
 6         // Start typing your C/C++ solution below
 7         // DO NOT write int main() function    
 8         int steps = 2 * nRows - 2;
 9         
10         string ret(s);
11         int retSize = 0;
12         for(int i = 0; i < nRows; i++)
13         {
14             int num = nRows - (i + 1) + nRows - (i + 1) - 1;
15             num++;
16             step[0] = num;
17             if (step[0] == 0)
18                 step[0] = steps;
19             step[1] = steps - num;
20             if (step[1] == 0)
21                 step[1] = steps;
22                 
23             int j = i;
24             int index = 0;
25             while(j < s.size())
26             {
27                 ret[retSize++] = s[j];
28                 if (j == j + step[index])
29                     break;
30                 j = j + step[index];
31                 index = 1 - index;
32             }
33         }    
34         
35         return ret;
36     }
37 };

 

 

posted @ 2012-11-18 17:40  chkkch  阅读(2891)  评论(0编辑  收藏  举报