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：
最开始题意理解不清楚，后来看了下面这组图以后就明白了，找规律解决即可。
nRows = 2 0 2 4 6 8 1 3 5 7 9
nRows = 3 0 4 8 12 16 1 3 5 7 9 11 13 15 2 6 10 14
nRows = 4 0 6 12 18 1 5 7 11 13 17 19 2 4 8 10 14 16 3 9 15
代码：
1 string convert(string s, int nRows) { 2 // IMPORTANT: Please reset any member data you declared, as 3 // the same Solution instance will be reused for each test case. 4 if(nRows == 1) 5 return s; 6 vector<string> tmp(nRows,""); 7 int step = 0, cur = 0; 8 int l = s.length(); 9 while(cur < l){ 10 if(step == 0){ 11 int i; 12 for(i = 0; i < nRows && cur+i < l; i++) 13 tmp[i] += s[cur+i]; 14 if(i < nRows) 15 break; 16 cur += nRows; 17 } 18 else{ 19 tmp[nRows-1-step] += s[cur]; 20 cur++; 21 } 22 step = (step+1)%(nRows-1); 23 } 24 string result = ""; 25 for(int i = 0; i < nRows; i++) 26 result += tmp[i]; 27 return result; 28 }