Converting HEX to DEC [duplicate] - c++

Question

This question already has answers here:
C++: Converting Hexadecimal to Decimal
(11 answers)
Closed 2 years ago.
I'm trying to use a C++ program to convert a hexadecimal value into a decimal value. Just can't come up with a working code.
This is the best thing I have come up with:
int main () {
string link;
string hex_code;
int dec_code;
int i;
int n = 6;
int num;
int hex;
cout << "Insert 1 of the HEX characters at a time:";
for (i = 0; i < n; i++) {
cin >> hex_code;
}
for (i = 0; i < n; i++) {
if (hex_code == "A") {
hex_code = 10;
}
else if (hex_code == "B") {
hex_code = 11;
}
else if (hex_code == "C") {
hex_code = 12;
}
else if (hex_code == "D") {
hex_code = 13;
}
else if (hex_code == "E") {
hex_code = 14;
}
else if (hex_code == "F") {
hex_code = 15;
}
else {
hex_code = hex_code;
}
num = hex * pow (16, i);
}
for (i = 0; i < n; i++) {
dec_code = dec_code + num;
}
cout << dec_code;
return 0;
}
Any help/feddback/opinions are welcome.
Edit: Thank you for all your help. Found the code I tryed to create, but failed, here: https://stackoverflow.com/a/27334556/13615474

Answer 1

There is a hex manipulator in iomanip library of C++
cout << "Insert 1 of the HEX characters at a time:";
for (i = 0; i < n; i++) {
int hexcode;
std::cin >> std::hex >> hexcode;
std::cout << hexcode << std::endl;
}
This would print decimal equivalent of given hex code

Answer 2

Hex to decimal conversion can be performed by reading the input number as a character array and performing the conversion arithmetic on each character.
Here is a working example for converting hexadecimal into decimal:
// File name: HexToDec.cpp
#include <iostream>
#include <cstring>
using namespace std;
int hexToDec(char hexNumber[]) {
int decimalNumber = 0;
int len = strlen(hexNumber);
for (int base = 1, i=(len-1); i>=0; i--, base *= 16) {
// Get the hex digit in upper case
char digit = toupper(hexNumber[i]);
if ( digit >= '0' && digit <='9' ) {
decimalNumber += (digit - 48)*base;
}
else if ( digit >='A' && digit <='F' ) {
decimalNumber += (digit - 55)*base;
}
}
return decimalNumber;
}
int main() {
char hexNumber[80];
// Read the hexadecimal number as a character array
cout << "Enter hexadecimal number: ";
cin >> hexNumber;
cout << hexNumber << " in decimal format = " << hexToDec(hexNumber) << "\n";
return 0;
}
Output:
Enter hexadecimal number: DEC
DEC in decimal format = 3564
More information:
https://www.geeksforgeeks.org/program-for-hexadecimal-to-decimal/

Answer 3

Here is a simple code fragment using a lookup table:
char c;
static const char hex_to_decimal[] = "0123456789ABCDEF";
std::cin >> c;
int decimal = 0;
for (decimal = 0; decimal < sizeof(hex_to_decimal) - 1; ++decimal)
{
if (hex_to_decimal[i] == c)
{
break;
}
}
Another conversion method:
std::cin >> c;
int decimal;
if (is_digit(c))
{
decimal = c - '0';
}
else
{
decimal = 10 + c - 'A';
}
The above code fragment assumes that the encoding has 'A'...'F' contiguous.
The first example is more portable.