[LeetCode] 541. Reverse String II

轉自LeetCode

Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and left the other as original.

Example:

Input: s = "abcdefg", k = 2
Output: "bacdfeg"

Restrictions:

1. The string consists of lower English letters only.
2. Length of the given string and k will in the range [1, 10000]

<Solution>

思考方式

• 把字串用 2k 個分成一組，前面 k 個反轉，後面不動

code 如下(參考資料)

Java

	class Solution {
	public String reverseStr(String s, int k) {
	char[] input = s.toCharArray();
	int i, j;
	char tmp;
	for(int start = 0; start < input.length; start += 2 * k) {
	i = start;
	j = Math.min(start + k - 1, input.length - 1);
	while(i < j) {
	tmp = input[i];
	input[i++] = input[j];
	input[j--] = tmp;
	}
	}
	return new String(input);
	}
	}

view raw reverseString2.java hosted with ❤ by GitHub