6.ZigZag Conversion(Graph, traverse)

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：图的遍历，先纵向，再横向。

图用string数组存储。

如果nRows=4，注意短的那列是倒序。

P      I      N

A  L  S  I  G

Y  A  H  R

P      I

如果nRows=2，全部是正序。

P  Y  ...

A  P  ...

class Solution {
public:
    string convert(string s, int numRows) {
        string sArray[numRows];
        int pChar = 0; //pointer to s
        int pRow = 0; //pointer to indicate row number
        
        while(1){
            pRow = 0;
            while(pRow < numRows && pChar != s.length()){ //traverse first colomn
              sArray[pRow++] += s[pChar++];
            }
            if(pChar == s.length()) return getReturnStr(sArray,numRows);
         
            pRow = numRows-2;
            while(pRow > 0 && pChar != s.length()){
              sArray[pRow--] += s[pChar++];
            }
            if(pChar == s.length()) return getReturnStr(sArray,numRows);
        }
    }
    string getReturnStr(string* sArray, int numRows){
        string ret = "";
        for(int i = 0; i < numRows; i++){
            ret += sArray[i];
        }
        return ret;
    }
};