# C Program for Balanced Parenthesis problem

## Balanced parenthesis problem

Today in this article we will learn how to solve Balanced Parenthesis problem.

Lets understand this with the help of an example:-

• Input: str = “[{}]”
Output: balanced

## Algorithm

• Initialize a character stack st
• Now traverse the string s
• If the current character is a starting bracket (‘(‘ or ‘{‘ or ‘[‘) then push it to stack st.
• If the current character is a closing bracket (‘)’ or ‘}’ or ‘]’) then check if the st is empty or not and also check if the top of the stack is the same opening brackets if it’s true then pop from stack otherwise put ans = false and break.
• At last check if stack is empty or not if its not empty return false
• At the end of the function return ans.
• In the main function inside if function check the string and print if the string is balanced or not

## C Code :-

Run
```#include <stdio.h>
#include <stdlib.h>

#define bool int

// structure of a stack node
struct sNode
{
char data;
struct sNode *next;
};
// Function to push an item to stack
void push (struct sNode **top_ref, int new_data);

// Function to pop an item from stack
int pop (struct sNode **top_ref);

bool isMatchingPair (char character1, char character2)
{

if (character1 == '(' && character2 == ')')
return 1;
else if (character1 == '{' && character2 == '}')
return 1;
else if (character1 == '[' && character2 == ']')
return 1;
else
return 0;
}

// Return 1 if expression has balanced Brackets
bool areBracketsBalanced (char exp[])
{

int i = 0;
// Declare an empty character stack
struct sNode *stack = NULL;

//Traverse the given expression to check matching
// brackets
while (exp[i])
{
// If the exp[i] is a starting bracket then push
// it
if (exp[i] == '{' || exp[i] == '(' || exp[i] == '[')
push (&stack, exp[i]);
if (exp[i] == '}' || exp[i] == ')'||exp[i] == ']')
{
if(stack == NULL)
return 0;
else if (!isMatchingPair (pop (&stack), exp[i]))
return 0;
}
i++;
}
if (stack == NULL)
return 1; // balanced
else
return 0; // not balanced
}

// Driver code
int main()
{
char exp[100] = "{()}[]";
// Function call
if (areBracketsBalanced (exp))
printf ("Balanced \n");
else
printf ("Not Balanced \n");
return 0;
}
// Function to push an item to stack
void push (struct sNode **top_ref, int new_data)
{
// allocate node
struct sNode *new_node  = (struct sNode *) malloc (sizeof (struct sNode));
if (new_node == NULL)
{
printf ("Stack overflow n");
getchar ();
exit (0);
}

// put in the data
new_node->data = new_data;
// link the old list off the new node
new_node->next = (*top_ref);
(*top_ref) = new_node;
}

// Function to pop an item from stack
int pop (struct sNode **top_ref)
{
char res;
struct sNode *top;
// If stack is empty then error
if (*top_ref == NULL)
{
printf ("Stack overflow n");
getchar ();
exit (0);
}

else
{
top = *top_ref;
res = top->data;
*top_ref = top->next;
free (top);
return res;
}

}```

## Output:-

`balanced`