Leetcode题解-6. ZigZag Conversion

Leetcode题解-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" .

思路：模拟Z型字符串的形成，用一个nRows大小的一维字符串矩阵存每一行，最后把每一行的字符串合并成一个输出的结果。把Z型左右压扁看成S型，每当到了第一行或者最后一行的时候就调转填字符的方向，例如nRows取3，从第一行填字符到第三行，然后调转填字符方向到第二行，行的顺序是1-2-3-2-1-2-3-2-1……时间复杂度是O(n)

string convert(string s, int numRows) {
	if(numRows == 1) return s;
	string *re = new string[numRows];
	int l = s.size();
	int row = 0;
	int turn = 0;
	for(int i = 0; i < l; i++){
		re[row] += s[i];
		if(row+1 == numRows) turn = 1;
		else if(row-1 == -1) turn = 0;
			
		if(turn == 0) row++;
		else if(turn == 1) row--;
	}
	string r = "";
	for(int i = 0; i < numRows; i++){
		r+=re[i];
	}
	return r;
}