LeetCode#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 s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:

P     I    N
A   L S  I G
Y A   H R
P     I

问题大意：在行数给定时，写出字符串“PAYPALISHIRING”的Z字形（zigzag）写法，有点像高中物理的沙漏和向前移动的纸带。

解题思路：遍历字符串，设置一个变量cur表示现在纵向的行号，在设置一个布尔变量down作为方向标志（down为真cur++,down为假cur--）。

#include<string>
#include<iostream>
using namespace std;

string convert(string s, int numRows){
	if (numRows == 1) return s;
	string rows[3];
	int cur = 0;
	bool down = true;
	for (int i = 0; i < s.size(); ++i){
		rows[cur] += s[i];
		if (cur == 0) down = true;
		else if (cur == (numRows - 1)) down = false;

		if (down) cur++;
		else cur--;
	}
	string ans;
	for (int i = 0; i < numRows; i++)
		ans += rows[i];
	return ans;
}

int main(){
	string s1 = "123456789";
	string result = convert(s1,3);

	cout << "zagzig输出是： " << result << endl;
	//139246837
	getchar();
}