
Problem:
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"
.
就是将一个字符串按照“之”字型表示后,按每行组合后输出新字符串。
在白头翁的博客里学习到了O(n)的算法。
就是创建nRows个string,将s对应坐标拷贝到每个string中,利用pushback操作。最后append连接输出。代码如下:
class Solution {
public:
string convert(string s, int nRows)
{
if (nRows <= || s.length() < )
return s; string *s_arr = new string[nRows];
int nCount = * (nRows - ); // 每个循环的轮回 也就是 2倍的nRows - 2 for (int i = ; i < s.length(); ++i)
{
s_arr[nRows - -abs(nRows - - (i%nCount))].push_back(s[i]);
} string str_result;
for (int i = ; i < nRows; ++i)
str_result.append(s_arr[i]); return str_result;
}
};
坐标对应是关键,数学逻辑思维确实要强。可以举个四行的例子试试。