C program to remove the brackets from a given input.

In C programming, removing brackets from mathematical expressions is a common string manipulation task. This involves processing the expression to eliminate parentheses while maintaining the correct mathematical meaning, especially handling sign changes when brackets are preceded by a minus sign.

Syntax

char* removeBrackets(char expression[]);

Algorithm

The algorithm to remove brackets follows these steps −

• Step 1: Read the input expression string
• Step 2: Traverse each character in the string
• Step 3: Copy non-bracket characters to result string
• Step 4: When encountering '(' preceded by '-', flip signs inside brackets
• Step 5: Skip bracket characters themselves

Example: Simple Bracket Removal

This example demonstrates basic bracket removal from a mathematical expression −

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

void removeBrackets(char input[], char output[]) {
    int i = 0, j = 0;
    int signFlip = 0;
    
    while (input[i] != '\0') {
        if (input[i] == '(') {
            // Check if preceded by minus sign
            if (i > 0 && input[i-1] == '-') {
                signFlip = 1;
                j--; // Remove the minus sign before bracket
            }
        }
        else if (input[i] == ')') {
            signFlip = 0;
        }
        else if (signFlip && (input[i] == '+' || input[i] == '-')) {
            // Flip the sign inside brackets preceded by minus
            output[j++] = (input[i] == '+') ? '-' : '+';
        }
        else {
            output[j++] = input[i];
        }
        i++;
    }
    output[j] = '\0';
}

int main() {
    char expression[100] = "(x+y)-(z-q)";
    char result[100];
    
    printf("Original expression: %s<br>", expression);
    removeBrackets(expression, result);
    printf("After removing brackets: %s<br>", result);
    
    return 0;
}

Original expression: (x+y)-(z-q)
After removing brackets: x+y-z+q

Example: Complex Expression

This example handles more complex expressions with multiple brackets −

#include <stdio.h>

int main() {
    char input[100], output[100];
    int i = 0, j = 0, signFlip = 0;
    
    printf("Enter mathematical expression: ");
    scanf("%s", input);
    
    while (input[i] != '\0') {
        if (input[i] == '(') {
            if (i > 0 && input[i-1] == '-') {
                signFlip = 1;
                j--; // Remove minus before opening bracket
            }
        }
        else if (input[i] == ')') {
            signFlip = 0;
        }
        else if (signFlip && (input[i] == '+' || input[i] == '-')) {
            output[j++] = (input[i] == '+') ? '-' : '+';
        }
        else {
            output[j++] = input[i];
        }
        i++;
    }
    output[j] = '\0';
    
    printf("Result: %s<br>", output);
    return 0;
}

Key Points

• Handle sign changes when brackets are preceded by minus operator
• Simple addition brackets can be removed directly
• Maintain proper string null termination
• Use array indexing for efficient character processing

Conclusion

Removing brackets from expressions in C requires careful handling of sign changes, especially when brackets follow a minus operator. The key is to flip signs inside such brackets while preserving the mathematical meaning of the expression.