ZigZag Conversion
Question
- leetcode: ZigZag Conversion| LeetCode OJ
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".
题解
可以发现首行和末行的重复周期都是 2 * nRows - 2,对于首行和末行之间的行,还会额外重复一次,重复的这一次距离本周期起始字符的距离是 2 * nRows - 2 - 2 * i 。
C++
class Solution {
public:
string convert(string s, int nRows) {
if (nRows <= 1 || s.length() == 0) //nRows=1 按下面会死循环
return s;
string ret = "";
const int len = s.size();
int lag = 2*nRows - 2; //循环周期
for (int i = 0; i < nRows; i++) {
for (int j = i; j < len; j += lag) {
ret += s[j];
if (i > 0 && i < nRows-1) { //非首行和末行时
int t = j + lag - 2*i;
if (t < len) {
ret += s[t];
}
}
}
}
return ret;
}
};