leetcode第6题ZigZag Conversion

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   NA P L S I I GY   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".

转载自：http://www.cnblogs.com/sanghai/p/3632528.html

Zigzag:即循环对角线结构（

0   8   16   1  79  1517   2 6 10 14 18   35  1113  19   4   12   20   

）

 

向下循环:nRows

斜角线循环:nRows-2(减去首尾两个端点)

重复

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string convert(string s,int nRows){

    if(nRows == 1)return s;

    string res[nRows];

    inti = 0, j, gap = nRows-2;

    while(i < s.size()){

        for(j = 0; i < s.size() && j < nRows; ++j) res[j] += s[i++];

        for(j = gap; i < s.size() && j > 0; --j) res[j] += s[i++];

    }

    string str ="";

    for(i = 0; i < nRows; ++i)

        str += res[i];

    returnstr;

}

　

技巧：创建res[nRows]保存每一行的字符串。

           利用向下循环和对角线循环组成一个大循环。