mirror of https://github.com/TheAlgorithms/C
120 lines
2.5 KiB
C
120 lines
2.5 KiB
C
/**
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* @file
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* @brief Convert hexadecimal number to octal number (with decimal intermediary)
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* @details
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* The input is valid from 0 to 0xFFFF_FFFF_FFFF_FFFF.
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*
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* At first, this program converts a hex string to an unsigned long long
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* decimal, and then to an octal string.
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*
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* When there is an invalid character in input string, this program stops
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* parsing and converts the string until that character.
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*
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* @see hexadecimal_to_octal.c
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*/
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#include <stdio.h> /// for printf() and fgets()
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#include <string.h> /// for memset()
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/**
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* @brief Convert a hexadecimal number to octal number.
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* @param hex Hexadecimal number to convert.
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* @returns A pointer to the converted octal string.
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*/
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const char *hex_to_oct(const char *hex)
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{
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#define MAX_OCT_STR_LEN 23 /* 17_7777_7777_7777_7777_7777 */
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static char octal[MAX_OCT_STR_LEN];
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memset(octal, '\0', MAX_OCT_STR_LEN); // Initialize as NULL string
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unsigned long long decimal = 0;
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int i = 0;
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int len;
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if (hex == NULL)
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{
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// Return an empty string
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return octal;
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}
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/* Hexadecimal to decimal conversion */
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while (*hex != '\n' && *hex != '\0')
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{
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char ch = *hex;
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if (ch >= '0' && ch <= '9')
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{
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ch -= '0';
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}
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else if (ch >= 'a' && ch <= 'f')
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{
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ch = ch - 'a' + 10;
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}
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else if (ch >= 'A' && ch <= 'F')
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{
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ch = ch - 'A' + 10;
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}
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else
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{
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printf("Invalid hexadecimal input: %c\n", ch);
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break;
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}
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decimal *= 16;
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decimal += ch;
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hex++;
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}
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/* Decimal to octal conversion */
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if (decimal == 0)
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{
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octal[0] = '0';
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len = 1;
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}
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else
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{
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i = 0;
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while (decimal > 0)
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{
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octal[i] = '0' + decimal % 8;
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i++;
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decimal /= 8;
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}
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len = i;
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}
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octal[len] = '\0';
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/* Reverse the octal string */
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for (i = 0; i < len / 2; i++)
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{
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char tmp = octal[i];
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octal[i] = octal[len - i - 1];
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octal[len - i - 1] = tmp;
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}
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return octal;
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}
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/**
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* @brief Main function
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* @returns 0 on exit
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*/
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int main()
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{
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#define MAX_HEX_STR_LEN 17 /* FFFF_FFFF_FFFF_FFFF */
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char hex[MAX_HEX_STR_LEN];
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/* Input hexadecimal number from user */
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printf("Enter any hexadecimal number: ");
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fgets(hex, MAX_HEX_STR_LEN, stdin);
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const char *octal = hex_to_oct(hex);
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printf("Hexadecimal number = %s\n", hex);
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printf("Octal number = %s\n", octal);
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return 0;
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}
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