#include <stdio.h>
#include <string.h>
 
    char binToHexDigit(const char bin[4]) {
        int digit = (bin[0] == '1' ? 8 : 0)
                  | (bin[1] == '1' ? 4 : 0)
                  | (bin[2] == '1' ? 2 : 0)
                  | (bin[3] == '1' ? 1 : 0);
        return (digit < 10 ? '0' : ('A'-10)) + digit;
    }
 
int main(void) {
	char *bin = "00001110001101101110100101010001010100001111";
	int len = strlen(bin);
	for (int i = 0 ; i < len ; i+=4) {
		printf("%c", binToHexDigit(&bin[i]));
	}
	printf("\n");
	return 0;
}
 

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