6. 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".

解题思路：模拟zigzag的移动方式(竖斜竖斜竖...)，用numRows个string，每次走到那个string时，在这后面把那个字符加上去。最后再把所有string拼起来就ok了

class Solution {
public:
    string convert(string s, int numRows) {
        if(numRows==1)return s;
        string* str=new string[numRows]; 
        int idx=0,step;
        for(int i=0;i<s.length();i++){
            str[idx].push_back(s[i]);
            if(idx==0)step=1;
            else if(idx==numRows-1)step=-1;
            idx+=step;
        }
        s.clear();
        for(int i=0;i<numRows;i++)
            s.append(str[i]);
        return s;    
    }
};