leetcode 6. ZigZag Conversion

1.题目

 

Total Accepted: 79300 Total
Submissions: 337482 Difficulty: Easy

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"

.

题目要求以反“N"的形状重新输出一个字符串。

2.思路 

首先我们创立一个字符串数组str[nRows],用以保留每一行的字符串。以题目为例，str[0]中保存的是"PAHN",str[nRows-1]中保存的是"YIR".

设置一个step参数，用以控制方向,row代表所走到的行数。在字符串走到最后一行之前，正向保存；走到最后一行之后，逆向保存至第0行，然后再正向保存，直至字符串遍历结束。

class Solution {
public:
string convert(string s, int numRows) {
string strs[numRows];
if(numRows <= 1) return s;
int row = 0, step = 1;
for(int i = 0 ; i < s.size(); i++){
strs[row].push_back(s[i]);
if(row == numRows - 1) step = -1;
if(row == 0) step = 1;
row += step;
}
string res = "";
for(auto str : strs) res = res + str;
return res;
}
};