【LeetCode】6. 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   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".

 

创建nRows个char数组，将s按照0,1,2,...,nRows-2,nRows-1,nRows-2,...,2,1,0的顺序，

将s中每个字符装入数组。

具体来说，数组下标先递增，直到nRows-1，则反向，直到0，再反向，……直到s字符全部装入各数组

再依次输出0~nRows-1个数组。

class Solution {
public:
    string convert(string s, int nRows) {
        if(nRows == 1)
            return s;
        string ret;
        vector<vector<char> > text(nRows, vector<char>());
        int tag = 1;    //1-ascend, -1-descend
        int ind = -1;
        for(int i = 0; i < s.size(); i ++)
        {
            ind += tag;
            text[ind].push_back(s[i]);
            if(ind == nRows-1)
                tag = -1;   //reach the tail, turn back
            else if(ind == 0)
                tag = 1;    //reach the head, turn back
        }
        for(int i = 0; i < nRows; i ++)
        {
            for(int j = 0; j < text[i].size(); j ++)
                ret += text[i][j];
        }
        return ret;
    }
};