Balanced Parenthesis in C
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Checking for balanced parentheses is a common problem in programming and is often used in compilers, text editors, and many other applications.
The idea is to ensure that for every opening parenthesis, there is a corresponding closing parenthesis, and they are properly nested.
One of the most efficient ways to solve this problem is by using a stack data structure.
The algorithm involves iterating through each character in the input string pushing opening parentheses onto the stack and popping them when a closing parenthesis is encountered.
Example:
Here's a simple C program to check for balanced parentheses using a stack:
// Program for balanced parentheses in C #include<stdio.h>Output:#include // Structure for stack typedef struct { char items[100]; int top; } Stack; // Initialize stack void init(Stack *s) { s->top = -1; } // Push operation void push(Stack *s, char c) { s->items[++s->top] = c; } // Pop operation char pop(Stack *s) { if (s->top == -1) { return '\0'; } return s->items[s->top--]; } // Check for balanced parentheses bool isBalanced(char *st) { Stack s; init(&s); while (*st) { if (*st == '(' || *st == '{' || *st == '[') { push(&s, *st); } else if (*st == ')' || *st == '}' || *st == ']') { char popped = pop(&s); if ((*st == ')' && popped != '(') || (*st == '}' && popped != '{') || (*st == ']' && popped != '[')) { return false; } } st++; } // Check if stack is empty return s.top == -1; } // Main function to test the program int main() { char st[100]; printf("Enter a string with parentheses: "); scanf("%s", st); if (isBalanced(st)) { printf("The parentheses are balanced.\n"); } else { printf("The parentheses are not balanced.\n"); } return 0; }
Enter a string with parentheses: 2 * ( 6 + 5 )2 * ( 6 + 5 ) The parentheses are balanced.
Examples:
Input: ((()))
Output: The parentheses are balanced.
Input: ((){}[])
Output: The parentheses are balanced.
Input: ({[)}
Output: The parentheses are not balanced.
Input: (({})
Output: The parentheses are not balanced.
This program uses a stack to keep track of opening parentheses and checks if each closing parenthesis matches the most recent opening parenthesis.
If the parentheses are balanced, it prints a message saying so; otherwise, it indicates that they are not balanced.
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