LeetCode 541: Reverse String II
Problem Description
Explanation
To solve this problem, we can iterate over the string in steps of 2k, and for each group of k characters, we reverse the first k characters. If the remaining characters are less than k but greater than 0, we reverse all of them. We can achieve this by swapping characters from the start and end of the group of k characters until we reach the middle.
Time Complexity: O(n) where n is the length of the string s. Space Complexity: O(1) as we are not using any extra space other than a few variables.
Solutions
class Solution {
public String reverseStr(String s, int k) {
char[] chars = s.toCharArray();
for (int i = 0; i < s.length(); i += 2*k) {
int start = i;
int end = Math.min(i + k - 1, s.length() - 1);
while (start < end) {
char temp = chars[start];
chars[start] = chars[end];
chars[end] = temp;
start++;
end--;
}
}
return new String(chars);
}
}Related LeetCode Problems
Loading editor...