NCTU LAB 07/05 NUM 3

#include <iostream>
#include <string.h>
#include <cmath>
using namespace std;

#define MAX 50

int countDigit(long long n){
    return floor(log10(n)+1);
}

char* hexToDec(char hex[]){
    int r, total=0;
    int length = strlen(hex);
    for(int i=0;i<hex[i]!='\0';i++){
        length--;
        if(hex[i]>='0' && hex[i] <='9'){
            r = hex[i] - 48;
        }else if(hex[i]>='a' && hex[i]<='f'){
            r = hex[i] - 87;
        }else if(hex[i]>='A' && hex[i]<='F'){
            r = hex[i] - 55;
        }
        total += r*pow(16, length);
    }
    int l = countDigit(total);
    char *result = new char[l];
    for(int i=0;i<l;i++){
        result[i] = total%10 + '0';
        total/=10;
    }
    return result;
}

void print(char* num){
    cout << "Result : ";
    for(int i=strlen(num)-1;i>=0;i--){
        cout << num[i];
    }
    cout << endl;
}

int main(){
    char num[MAX];
    cout << "Enter a hexadecimal number : ";
    while(cin >> num){
        char* res = hexToDec(num);
        print(res);
        free(res);
        cout << "Enter a hexadecimal number : ";
    }
    return 0;
}