LeetCode算法題——ZigZag Conversion

Description:

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"

Zigzag:即循環對角線結構（

0				8				16
1			7	9			15	17
2		6		10		14		18
3	5			11	13			19
4				12				20

）

算法思想：

向下循環

斜對角循環：gap=nRows-2(去除端點)

C++ Implements:

string convert(string s, int numRows) {

        if(numRows==1) return s;

        string str[numRows];

        int i=0,gap=numRows-2;

        while(i<s.size()){

            for(int j=0;j<numRows&&i<s.size();j++){

                str[j]+=s[i++];

            }

            for(int j=gap;j>0&&i<s.size();j--){

                str[j]+=s[i++];

            }

        }

        string res="";

        for(int j=0;j<numRows;j++){

            res+=str[j];

        }

        return res;

    }