ZigZag ConversionDec
6 '11
6 '11
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",
should return
3)"PAHNAPLSIIGYIR"
.
思路:
zigzag的意思是"之"字形,zigzag conversion也就是按"N"字母的样子来重新安排字符串中字符的位置,并合并成一个新的字符串。nRows则表示"N"的高度,也就是每一竖列有nRows个字符。
我采用的是一个比较简单的方法,创建nRows个string,并将老字符串中字符依次写入新string中,写完之后将nRows个string合并成一个,问题就解决了。算法的复杂度为O(n)。
代码如下:
class Solution { public: string convert(string s, int nRows) { if (nRows <= 1 || s.length() < 2) return s; string *s_arr = new string[nRows]; int nCount = 2 * (nRows - 1); for (int i = 0; i < s.length(); ++i) { s_arr[nRows - 1 -abs(nRows - 1 - (i%nCount))].push_back(s[i]); } string str_result; for (int i = 0; i < nRows; ++i) str_result.append(s_arr[i]); return str_result; } };