Description
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)
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".
Solution
找规律
class Solution {
public String convert(String s, int numRows) {
if (s == null || numRows < 1) {
return null;
}
StringBuilder sb = new StringBuilder();
int largeStep = Math.max((numRows - 1) << 1, 1); // important
int smallStep = largeStep;
for (int i = 0; i < numRows; ++i) {
for (int j = i; j < s.length(); j += largeStep) {
sb.append(s.charAt(j));
if (smallStep > 0 && smallStep < largeStep
&& j + smallStep < s.length()) {
sb.append(s.charAt(j + smallStep));
}
}
smallStep -= 2;
}
return sb.toString();
}
}
