5.2.3.2 Rotate String
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2023-12-01
一、题目
Given a string and an offset, rotate string by offset. (rotate from left to right)
Example
Given
"abcdefg"
.offset=0 => "abcdefg" offset=1 => "gabcdef" offset=2 => "fgabcde" offset=3 => "efgabcd"
Challenge
Rotate in-place with O(1) extra memory.
给定一个字符串和一个偏移量,根据偏移量旋转字符串(从左向右旋转)
二、解题思路
常见的翻转法应用题,仔细观察规律可知翻转的分割点在从数组末尾数起的offset位置。先翻转前半部分,随后翻转后半部分,最后整体翻转。
三、解题代码
public class Solution {
/*
* param A: A string
* param offset: Rotate string with offset.
* return: Rotated string.
*/
public char[] rotateString(char[] A, int offset) {
if (A == null || A.length == 0) {
return A;
}
int len = A.length;
offset %= len;
reverse(A, 0, len - offset - 1);
reverse(A, len - offset, len - 1);
reverse(A, 0, len - 1);
return A;
}
private void reverse(char[] str, int start, int end) {
while (start < end) {
char temp = str[start];
str[start] = str[end];
str[end] = temp;
start++;
end--;
}
}
}