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This approach revolves around using a stack to efficiently identify and remove the substrings "AB" and "CD" from the given string. By traversing each character of the string:
The characters that remain on the stack are the ones that could not form any removable patterns, thus forming the result string.
Time Complexity: O(n), where n is the length of the string.
Space Complexity: O(n), to store the stack elements, based on the worst case where no pairs are removed.
1#include <stdio.h>
2#include <string.h>
3
4int minLengthAfterRemovals(const char *s) {
5 char stack[100
This implementation carries out a linear traversal of the string and uses a simple array to simulate stack operations. The stack's top is managed using an integer (top) that tracks the index of the last element.
This technique uses a two-pointer approach to reduce the string by altering it in place. The core idea is to selectively overwrite positions in the string:
After reaching the end of the string, the length of the string from the start to the write pointer represents the reduced string length.
Time Complexity: O(n), dependent on examining each character once.
Space Complexity: O(1), as no additional data structures are used.
public class MinLengthString {
public static int MinLengthAfterRemovals(string s) {
char[] arr = s.ToCharArray();
int write = 0;
for (int read = 0; read < arr.Length; read++) {
if (write > 0 && ((arr[read] == 'B' && arr[write - 1] == 'A') || (arr[read] == 'D' && arr[write - 1] == 'C'))) {
write--;
} else {
arr[write++] = arr[read];
}
}
return write;
}
public static void Main(string[] args) {
string s = "ABFCACDB";
Console.WriteLine(MinLengthAfterRemovals(s));
}
}Using character arrays in C#, this solution directly modifies the sequence of characters to simulate a condensed version of the input after removing specified patterns.