Minimum number of basic logic gates required to realize given Boolean expression

Given a string S of length N representing a boolean expression, the task is to find the minimum number of AND, OR, and NOT gates required to realize the given expression.

Examples:

Input: S = "A+B.C"
Output: 2
Explanation: Realizing the expression requires 1 AND gate represented by '.' and 1 OR gate represented by '+'. 

Input: S = "(1 - A). B+C"
Output: 3
Explanation: Realizing the expression requires 1 AND gate represented by '.' and 1 OR gate represented by '+' and 1 NOT gate represented by '-'. 

Approach: Follow the steps below to solve the problem:

1. Iterate over the characters of the string.
2. Initialize, count of gates to 0.
3. If the current character is either '.' or '+', or '1', then increment the count of gates by 1
4. Print the count of gates required.

Below is the implementation of the above approach:

3

Time Complexity: O(N)
Auxiliary Space: O(1)