Prompt Title: Bracket Matching Program.

Certainly! Here's an explanation of the shorter program:

1. We include the necessary header file stdio.h for standard input/output functions.

2. In the main() function, we declare two character arrays: expr to store the input expression and stack to simulate the stack. We also initialize the stack's top index top to -1.

3. We prompt the user to enter an expression using printf().

4. We read the expression using fgets(), which ensures the input does not exceed the buffer size and avoids buffer overflow vulnerabilities.

5. We initialize a loop variable i to 0, which we will use to iterate through each character of the expression.

6. Inside the loop, we check each character of the expression one by one:

   • If the character is an opening bracket ('(', '[', '{'), we push it onto the stack by incrementing top and storing the character in stack[top].

   • If the character is a closing bracket (')', ']', '}'), we perform the following checks:

     • If top is less than 0, it means there are no matching opening brackets in the stack. Thus, the brackets are not balanced, and we print the corresponding message using printf(). We then return from the main() function, terminating the program.

     • Otherwise, we retrieve the topmost character from the stack by assigning stack[top] to bracket and decrement top to simulate popping the bracket from the stack. We then compare the popped bracket with the current closing bracket to check if they match. If they don't match, we print the message that the brackets are not balanced and return from the main() function.

   • We increment i to move to the next character of the expression.

7. After the loop, we perform a final check:

   • If top is less than 0, it means all the opening brackets have been matched and popped from the stack, and there are no remaining unmatched brackets. In this case, we print the message that the brackets are balanced using printf().

   • If top is not less than 0, it means there are unmatched opening brackets remaining in the stack. Hence, the brackets are not balanced, and we print the corresponding message.

8. Finally, we return 0 to indicate successful program execution.

The program uses a simple stack implementation using an array to track the opening brackets encountered. It compares the closing brackets with the last opening bracket encountered to determine if the brackets are balanced or not.