Leetcode ZigZag Conversion

Leetcode ZigZag Conversion

做这道题遇到几个点，记录如下

1. numRows <= 1的情况需要注意
2. C++ string::append不可附加字符char,顾可以考虑用push_back或+=
3. java的话最好用StringBuffer,可本地修改
4. 这道题的思路有些像波的传播+钟摆采样

class Solution {
public:
    string convert(string s, int numRows) {
        string* buffer = new string[numRows];
        if(numRows <= 1)
        {
            return s;
        }
        int index = 0, step = 1;
        for(int i = 0; i < s.length(); i++)
        {
            if(index == 0)
            {
                step = 1;
            }else if(index == numRows - 1){
                step = -1;
            }
            buffer[index] += s[i];
            index += step;
        }
        //string result;    /**for saving space **/
        s.clear();
        for(int i = 0; i < numRows; i++)
        {
            s.append(buffer[i]);
        }
        delete[] buffer;
        return s;
    }
};

附上说明

void push_back ( char c );

Append character to string

Appends a single character to the string content, increasing its size by one.

To append more than one character at a time, refer to either member append or operator+=.