code2

#include <stdio.h>
#include <stdbool.h>
#include <string.h>

// Structure to represent a stack
struct Stack {
    char data[100];
    int top;
};

// Function to initialize an empty stack
void initStack(struct Stack* s) {
    s->top = -1;
}

// Function to push an element onto the stack
void push(struct Stack* s, char c) {
    s->data[++s->top] = c;
}

// Function to pop an element from the stack
char pop(struct Stack* s) {
    if (s->top == -1) {
        return '\0';
    }
    return s->data[s->top--];
}

// Function to check if a character is an opening parenthesis
bool isOpening(char c) {
    return (c == '(' || c == '{' || c == '[');
}

// Function to check if a character is a closing parenthesis
bool isClosing(char c) {
    return (c == ')' || c == '}' || c == ']');
}

// Function to check if two characters form a valid pair of parentheses
bool isValidPair(char open, char close) {
    return (open == '(' && close == ')') ||
           (open == '{' && close == '}') ||
           (open == '[' && close == ']');
}

// Function to check the validity of parentheses in a string
bool isValidParentheses(char* str) {
    struct Stack stack;
    initStack(&stack);

    int len = strlen(str);
    for (int i = 0; i < len; i++) {
        char current = str[i];
        if (isOpening(current)) {
            push(&stack, current);
        } else if (isClosing(current)) {
            if (stack.top == -1 || !isValidPair(stack.data[stack.top], current)) {
                return false;  // Unmatched or invalid pair
            } else {
                pop(&stack);
            }
        }
    }

    return (stack.top == -1);  // Stack should be empty if all parentheses are matched.
}

int main() {
    char input[100];
    printf("Enter a string with parentheses: ");
    scanf("%s", input);

    if (isValidParentheses(input)) {
        printf("Valid parentheses\n");
    } else {
        printf("Invalid parentheses\n");
    }

    return 0;
}