[LC] 541. Reverse String II

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:

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

class Solution {

    public String reverseStr(String s, int k) {

        int i = 0;

        char[] charArr = s.toCharArray();

        while (i < charArr.length) {

            int j = Math.min(i + k - 1, charArr.length - 1);

            swap(i, j, charArr);

            i += 2 * k;

        }

        return new String(charArr);

    }

    private void swap(int i, int j, char[] charArr) {

        while (i < j) {

            char temp = charArr[i];

            charArr[i] = charArr[j];

            charArr[j] = temp;

            i += 1;

            j -= 1;

        }

    }

}

巴特西

[LC] 541. Reverse String II

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