6.[leetcode] 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".

原题链接：https://leetcode.com/problems/zigzag-conversion/

Analysis & Solution

There exits pattern in the ZigZag Conversion. The indexs at i row follows patterns:

Let DiffConstant = 2*row - 2

i = 0: the difference = DiffConstant

i = 1: the differences = 2(row-1) - 2, DiffConstant - (2(row-1) - 2).

i = 2: the differences = 2(row-2) - 2, DiffConstant - (2(row-2) - 2).

i = k: the differences = 2(row-k) - 2, DiffConstant - (2(row-k) - 2) = 2k

 public String convert(String s, int numRows) {

        if(numRows == 1){

            return s;

        }

        int diffConstant = 2*numRows - 2, i, index;

        StringBuffer res = new StringBuffer();

        for(i = 0; i < numRows; i++){

            index = i;

            boolean isEven = true;

            while(index < s.length()){

                res.append(s.charAt(index));

                if(i == 0 || i == numRows -1){

                    index += diffConstant;

                }else{

                    if(isEven){

                        index += 2*(numRows-i) - 2;

                    }else{

                        index +=  2*i;

                    }

                    isEven = !isEven;

                }

            }

        }

        return res.toString();

    }

巴特西

6.[leetcode] ZigZag Conversion

Analysis & Solution

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