Minimum Length of String After Operations

class Solution {
public:
    int minLen(string str) {
        int visible = 0;
        int bitMask = 0;
        int bitPos;

        // Loop over characters to modify bit masks
        for (int idx = 0; idx < str.length(); idx++) {
            bitPos = 1 << (str[idx] - 'a');
            visible |= bitPos;
            bitMask ^= bitPos;
        }

        int minLength = 0;

        // Calculate required minimum total length
        while (visible) {
            bitPos = visible & (visible - 1);
            minLength += 2 - ((bitMask & (visible - bitPos)) != 0);
            visible = bitPos;
        }

        return minLength;
    }
};

This solution implements a function in C++ to determine the minimum length of a string after applying a series of operations defined by bit manipulation techniques. Here's how the solution works:

1. Initialize visible and bitMask to track which characters have been seen and their occurrence counts respectively.
2. Using a loop, iterate over each character in the input string.
   • Calculate bitPos, which is a bitmask representing the current character's position in the alphabet.
   • Update visible to include the current character's bitmask.
   • Use XOR operation on bitMask with bitPos to toggle the character's count between even and odd.
3. Initialize minLength to zero for calculating the result.
4. For each character that has been seen (visible is not zero):
   • Determine which characters need to be considered for pairing off by manipulating the bit positions.
   • Increase minLength by 2 for most characters, except decrease it by 1 if the character has an odd occurrence by checking bitMask.
5. Finally, return minLength which is the calculated minimum length of the string after operations.

Using bit manipulation allows for an efficient mechanism to handle and compute character occurrences leading to the calculation of minimum string length according to given operational rules. This approach ensures a compact and optimal solution, leveraging bitwise operations for fast computation.

class Solution {

    public int minStringLength(String input) {
        int activeBits = 0;
        int flipBits = 0;
        int bitMask;

        for (int i = 0; i < input.length(); i++) {
            bitMask = 1 << (input.charAt(i) - 'a');
            activeBits |= bitMask;
            flipBits ^= bitMask;
        }

        int minLength = 0;

        while (activeBits > 0) {
            bitMask = activeBits & (activeBits - 1);
            minLength += 2 - ((flipBits & (activeBits - bitMask)) != 0 ? 1 : 0);
            activeBits = bitMask;
        }

        return minLength;
    }
}

The provided Java solution is designed to compute the minimum length of a string after performing specific operations that involve flipping bits to represent characters. The key components and actions in the solution are as follows:

• Initialize variables activeBits and flipBits to keep track of which bits (characters) have been seen and flipped respectively.
• Use a bit-wise operation logic that involves a for loop iterating over characters in the input string. In each iteration:
  • Calculate a bitMask for the current character to identify its position in the alphabet using a shift operation.
  • Update activeBits using an OR operation on bitMask to track characters present in the string.
  • Update flipBits using an XOR operation on bitMask to manage flip states of characters.
• Determine the minimal length after all characters are processed:
  • A while loop is used where the condition checks if there are still active bits.
  • In each iteration, update activeBits by turning off the rightmost bit, and increment minLength based on the condition whether the character was flipped an odd or even number of times.
  • The expression within incrementing minLength uses a bitwise AND and a subtraction to determine if the flipped state should adjust the count by 1 or 2.

Overall, the logic cleverly uses bitwise operations to efficiently calculate the minimal length of the string by accounting for each character's appearance and its number of flips, thus determining how it contributes to the string's final length after all operations are applied. This approach ensures an optimal runtime with a clear focus on bitwise manipulation for string character analysis.

class Solution:
    def findMinimumLength(self, str_input: str) -> int:
        current_mask = 0
        even_odd_mask = 0
        single_bit_mask = 0

        for character in str_input:
            single_bit_mask = 1 << (ord(character) - ord('a'))
            current_mask |= single_bit_mask
            even_odd_mask ^= single_bit_mask

        calculated_length = 0

        while current_mask > 0:
            single_bit_mask = current_mask & (current_mask - 1)
            calculated_length += 2 - ((even_odd_mask & (current_mask - single_bit_mask)) != 0)
            current_mask = single_bit_mask

        return calculated_length

The Python code provided defines a method within a class that calculates the minimum length of a string after performing certain operations. The method findMinimumLength uses bit manipulation to efficiently track and process the characters of the input string to determine the resulting length. Here’s a breakdown of how the method works:

• Initialization of Masks: The method begins by initializing three integer variables current_mask, even_odd_mask, and single_bit_mask to keep track of different aspects of the characters in the string.
• Character Processing:
  • Loop through each character in the input string.
  • For each character, calculate a single_bit_mask which is based on the character's position in the alphabet (using bitwise shift).
  • Update current_mask with this single_bit_mask using bitwise OR, to record the occurrence of the character.
  • Update even_odd_mask using bitwise XOR to toggle the presence of the character and assist in tracking even and odd occurrences.
• Calculate Minimum Length:
  • Initiate calculated_length to count the resultant string's length.
  • Use a while loop to iterate as long as current_mask is greater than zero.
  • In each iteration, adjust single_bit_mask to exclude the rightmost 1 bit from current_mask.
  • Increase calculated_length based on whether the toggled even-odd occurrence of characters (tracked by even_odd_mask) is still one after updating single_bit_mask.
  • Update current_mask to be the new single_bit_mask for the next iteration.
• Return Calculated Length: After processing all characters and their occurrences, return calculated_length, representing the minimum length of the string after performing the operations.

The method meticulously combines bit manipulation techniques to track character occurrences and frequencies efficiently, ensuring an optimal solution to find the minimum length of the processed string.