求助 十六进制和十进制的转换
我做得一个题目要求能够自由转换十进制和十六进制，现在十进制到十六进制的转换没有问题，但是十六进制到十进制的转换不成功，有哪位大大能帮我看一下，究竟要在哪儿改正，问题在哪儿？

HexaInt.h

#ifndef HEXAINT_H_
#define HEXAINT_H_

#include <iostream>
using namespace std;

class HexaInt{
private:
unsigned int decimal;
char* hex;

public:
HexaInt(int decimal=0);
HexaInt(const HexaInt& copy);
~HexaInt();

void setDecimal(int decimal);
int getDecimal()const;
void decToHex();
void hexToInt();

HexaInt operator+(const HexaInt& other)const;
HexaInt operator-(const HexaInt& other)const;
HexaInt operator*(const HexaInt& other)const;
HexaInt operator/(const HexaInt& other)const;
HexaInt operator%(const HexaInt& other)const;
HexaInt& operator=(const HexaInt& other);
char& operator[](int i);

friend ostream& operator<< (ostream& out, const HexaInt& h);
friend istream& operator>> (istream& in, HexaInt& h);
};

#endif /*HEXAINT_H_*/

HexaInt.cpp

#include "HexaInt.h"

HexaInt::HexaInt(int decimal){
int zahl = sizeof(unsigned int)*2;
this->hex = new char[zahl];
this->decimal = decimal;
decToHex();
}

HexaInt::~HexaInt(){
delete[] this->hex;
}

HexaInt::HexaInt(const HexaInt& other){
this->decimal = other.decimal;
int zahl = sizeof(unsigned int)*2;
hex = new char[zahl];
decToHex();
}

void HexaInt::decToHex(){
sprintf(this->hex, "%x", this->decimal);
}

void HexaInt::hexToInt(){
sscanf(this->hex, "%x", &this->decimal);
}

void HexaInt::setDecimal(int d){
   this->decimal = d;
   decToHex();
}

int HexaInt::getDecimal()const{
return this->decimal;
}

HexaInt HexaInt::operator+(const HexaInt& other)const{
HexaInt result;
result.decimal = this->decimal+other.decimal;
sprintf(result.hex, "%x", result.decimal);
return result;
}

HexaInt HexaInt::operator-(const HexaInt& other)const{
HexaInt result;
result.decimal = this->decimal-other.decimal;
sprintf(result.hex, "%x", result.decimal);
return result;
}

HexaInt HexaInt::operator*(const HexaInt& other)const{
HexaInt result;
result.decimal = this->decimal*other.decimal;
sprintf(result.hex,"%x", result.decimal);
return result;
}

HexaInt HexaInt::operator/(const HexaInt& other)const{
HexaInt result;
result.decimal = this->decimal/other.decimal;
sprintf(result.hex,"%x",result.decimal);
return result;
}

HexaInt HexaInt::operator%(const HexaInt& other)const{
HexaInt result;
result.decimal = this->decimal%other.decimal;
sprintf(result.hex,"%x",result.decimal);
return result;
}

ostream& operator<<(ostream& s, const HexaInt& h){
cout << "DEZ: " << h.decimal <<" HEX: " << h.hex << endl; 
 
return s;
}

istream& operator>>(istream& s, HexaInt& h){
int newValue;
s >> newValue;
h.setDecimal(newValue);
return s;
}

char& HexaInt::operator[](int i){
return this->hex[i];
}

HexaInt& HexaInt::operator=(const HexaInt& other){
if(&other != this){
delete[] hex;
this->decimal = other.decimal;
int zahl = sizeof(unsigned int)*2;
this->hex = new char[zahl];
decToHex();
}
return *this;
}

main.cpp

#include "HexaInt.h"

int main(){

HexaInt hex1(42);
cout << "Hex1-> " << hex1;

HexaInt hex2(hex1);
hex1 = hex2;
cout << "Hex2-> " << hex2;
cout << "Hex1 "<< hex1[0] << endl;
cout << "Hex2 "<< hex2[0] << endl;

hex1.setDecimal(18);
cout << "Hex1-> " << hex1;
cout << "Hex2-> " << hex2;

hex2.setDecimal(237);
cout << "Hex1-> " << hex1;
cout << "Hex2-> " << hex2;

HexaInt hex3 = hex1 + hex2;
cout << "Hex3-> " << hex3;


HexaInt a;
a[0] = 'F';
cout << "a-> " << a;
HexaInt b(a);
cout << "b-> " << b;

return 0;
}

结果是：
Hex1-> DEZ: 42 HEX: 2a
Hex2-> DEZ: 42 HEX: 2a
Hex1 2
Hex2 2
Hex1-> DEZ: 18 HEX: 12
Hex2-> DEZ: 42 HEX: 2a
Hex1-> DEZ: 18 HEX: 12
Hex2-> DEZ: 237 HEX: ed
Hex3-> DEZ: 255 HEX: ff
a-> DEZ: 0 HEX: F
b-> DEZ: 0 HEX: 0
最后的两个转换无法进行，谢谢！ 求助?十六进制 求助 进制转换
[解决办法]
HexaInt a; //a是用HexaInt(int decimal=0);造的，所以decimal=0；
a[0] = 'F'; //使用char& HexaInt::operator[](int i){ return this->hex[i];} 的，
//但是decimal的值是 0；造成了 hex 和decimal 不一致。
cout << "a-> " << a;

HexaInt b(a); //b是用HexaInt(const HexaInt& copy);造的，所以b的decimal也0
cout << "b-> " << b;

建改:
加一hex造函.
HexaInt(const char* hexstr=0)
{
int zahl = sizeof(unsigned int)*2;
//空有少，因有'\0'束符，所以多加
zahl += 4;

hex = new char[zahl];

strcpy(hex,hexstr);

//要hex 字符 decimal, 有。

decimal = 0;
const char *phex = hexstr;
while (*phex){
decimal += hextodec(*phex);
decimal *= 16;
}

}

int hextodec(char h)
{
if ('0'<=ch && ch <='9')
return ch-'0';
if ('a'<=ch && ch <='f')
return 10+(ch-'a');
if ('A'<=ch && ch <='F')
return 10+(ch-'A');

return -1;
}

最後,就可以造a
HexaInt a("F");


以上代,提供思路,不保正.
[解决办法]
strtol
_ltoa