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In this approach, we directly manipulate the string representation by considering it as a character array (or list in some languages) for in-place modification. We handle the string in chunks of 2k and reverse the first k characters of each chunk.
Time Complexity: O(n), where n is the length of the string.
Space Complexity: O(1), as we are reversing in place.
1def reverse_string(s, k):
2 s = list(s) # Convert to list to allow modification
3 for start in range(0, len(s), 2 * k):
4 s[start:start + k] = reversed(s[start:start + k])
5 return ''.join(s)
6
7s = "abcdefg"
8k = 2
9print(reverse_string(s, k)) # Output: "bacdfeg"In Python, this solution converts the string to a list for easy modification. The slice reversing makes it intuitive to handle the required range, converting back to a string at the end of the process.
In this approach, we use a StringBuilder (or equivalent structure in the respective programming languages) to construct the final output. This approach is effective because handling mutable strings directly supports efficient character manipulation operations.
Time Complexity: O(n), where n is the length of the string.
Space Complexity: O(1) as we operate directly on the input array.
1using System.Text;
public class Solution {
public static string ReverseString(string s, int k) {
var stringBuilder = new StringBuilder(s);
for (int start = 0; start < s.Length; start += 2 * k) {
int end = Math.Min(start + k, s.Length);
string reversedPart = new string(s.Substring(start, end - start).ToCharArray().Reverse().ToArray());
stringBuilder.Remove(start, end - start).Insert(start, reversedPart);
}
return stringBuilder.ToString();
}
public static void Main() {
string s = "abcdefg";
int k = 2;
Console.WriteLine(ReverseString(s, k)); // Output: "bacdfeg"
}
}This C# solution uses StringBuilder for mutable string operations. It manages the reversal logic by first creating a reversed substring and then integrating it back into the builder efficiently.