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Utilize a stack to handle the nested or paired parentheses efficiently. By pushing characters onto a stack until a closing parenthesis is encountered, then reversing the needed substring, you can leverage the stack's LIFO properties to achieve the desired result.
Time Complexity: O(n).
Space Complexity: O(n) due to the stack usage for storing characters.
1import java.util.Stack;
2
3public class ReverseParentheses {
4 public String reverseParentheses(String s) {
5 Stack<Character> stack = new Stack<>();
6 for (char c : s.toCharArray()) {
7 if (c != ')') stack.push(c);
8 else {
9 StringBuilder sb = new StringBuilder();
10 while (stack.peek() != '(') {
11 sb.append(stack.pop());
12 }
13 stack.pop(); // pop '('
14 for (char rc : sb.toString().toCharArray()) stack.push(rc);
15 }
16 }
17 StringBuilder result = new StringBuilder();
18 while (!stack.isEmpty()) result.append(stack.pop());
19 return result.reverse().toString();
20 }
21
22 public static void main(String[] args) {
23 ReverseParentheses rp = new ReverseParentheses();
24 System.out.println(rp.reverseParentheses("(u(love)i)"));
25 }
26}
27This Java solution uses a stack to efficiently reverse substrings within parentheses. By iteratively processing the string and using the stack to manage open and close parenthesis contexts, it provides a clean logic flow to manage reversal operations appropriately.
This approach involves separately building the result string in a single pass using an auxiliary data structure to track position swaps. The use of local in-string reversals enables an efficient and clean traversal building mechanism.
Time Complexity: O(n).
Space Complexity: O(n), using additional space for parentheses pair tracking and intermediate char arrays.
using System.Collections.Generic;
public class ReverseParentheses {
public string ReverseParentheses(string s) {
Stack<int> stack = new Stack<int>();
int[] pair = new int[s.Length];
for (int i = 0; i < s.Length; i++) {
if (s[i] == '(') stack.Push(i);
else if (s[i] == ')') {
int j = stack.Pop();
pair[i] = j;
pair[j] = i;
}
}
char[] result = new char[s.Length];
int idx = 0, dir = 1;
for (int i = 0; i < s.Length; i += dir) {
if (s[i] == '(' || s[i] == ')') {
i = pair[i];
dir = -dir;
} else {
result[idx++] = s[i];
}
}
return new string(result, 0, idx);
}
public static void Main(string[] args) {
ReverseParentheses rp = new ReverseParentheses();
Console.WriteLine(rp.ReverseParentheses("(ed(et(oc))el)"));
}
}
This C# implementation uses an array for parenthesis pair tracking and a stack for real-time index management. The strategic index skipping and direct character assignment minimize additional restructuring operations.