Convert Binary String to Signed 32-bit Integer

Task

Implement the function bin_to_dec_signed

• Write a function that takes a null-terminated char[] consisting of ASCII '0' and '1' characters ($\text{length}\le 32$), and return the signed 32-bit integer it represents (using 2’s complement for negatives)
• if the string is less than 32 characters, sign-extend the most significant bit (the leftmost bit) up to 32 characters
• The function signature is

// Given a char[] of ASCII '0' and '1' (length ≤ 32), return the signed 32-bit integer it represents
// If the string is shorter than 32, assume leading 1's 
void bin_to_dec_signed(char str[]);

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Test

Compiling

gcc bin_to_dec_signed.c -o bin_to_dec_signed
./bin_to_dec_signed

Examples

$ ./bin_to_dec_signed
110
-2
00000000000000000000000000000001
1
11111111111111111111111111111111
-1
10000000000000000000000000000000
-2147483648

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Code

#include <string.h>
 
void bin_to_dec_signed(char str[]){
	int max_len = strlen(str);
	int result = 0;
	int value_at_index = 1;
	for(int i = max_len - 1; i > 0; i--, value_at_index *= 2){
		if(str[i] == '1'){
			result += value_at_index;
		}
	}
	
	if(str[0] == '1'){
		// value_at_index has already been updated to the next digit by the loop
		result -= value_at_index;
	}
	
	printf("%d\n", result);
}