题意:
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”.
题目大致意思就是说输入一个字符串s和一个整数row,然后将s排成一个row行的“Z”字形, 最后返回这个“Z”字形字符串。
解法:归纳起来就是找规律,见以下ac代码。
class Solution {
public String convert(String s, int num) {
StringBuilder ans = new StringBuilder();
if (num <= 1 || s.length() <= num) return s;
for (int i = 0; i < num; i ++) {
for (int j = i; j < s.length(); j += 2 * num - 2){
ans = ans.append(s.charAt(j));
if (i % num != 0 && i % num != (num - 1)){
int tmp = 2 * (num - i - 2) + 2 + j;
if (tmp < s.length())
ans = ans.append(s.charAt(tmp));
}
}
}
return ans.toString();
}
}
坑点:
1、StringBuilder要比StringBuffer快。
2、如果题目给定的row大于或等于数组长度的话直接返回s就可以了。
3、写代码的时候头脑一定要清醒(。。)。