c++ - 将有符号和无符号十六进制转换为 dec 和 dec 为十六进制 C++

Question

我必须编写一个程序，将无符号十六进制转换为十进制，将十进制转换为十六进制，将有符号十六进制转换为十进制，将十进制转换为十六进制，而不使用流过滤器“十六进制”和“十进制”。我的程序适用于 hex 到 dec 和 dec 到 hex 的无符号转换，但不适用于 SIGNED hex 到 dec 和 dec 到 hex。任何帮助将不胜感激。提前谢谢您!

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

void convertDecToHex(unsigned hexNumber);
int convertHexToDec(char hex[], unsigned numberSize);
signed SignedDecToHex (signed DecNumberSigned);
signed SignedHexToDec (int number);

int main (){
    unsigned choice, numberSize = 0, hexNumber;
    signed DecNumberSigned;
    char hex[100000];
    string number, HexNumberSigned;

    while (1){
        cout << "Enter 1 to convert from unsigned Dec to Hex:" << endl <<     "Enter 2 to convert from unsigned Hex to Dec:" 
            << endl << "Enter 3 to convert from signed Dec to Hex:"<< endl    << "Enter 4 to convert from signed Hex to Dec:" << endl ;
        cin >> choice;

        if (choice == 1){
            cout << "Enter unsigned dec # to convert to hex: " << endl;
            cin >> hexNumber;
            convertDecToHex( hexNumber);
        }//1
        if (choice == 2){
            cout << "Enter unsigned hex # to convert to dec: " << endl;
            cin >> number;
            numberSize = number.size();
            strcpy(hex, number.c_str());
            cout << convertHexToDec(hex, numberSize) << endl;
        }//2
        if (choice == 3){
            cout << "Enter signed dec to convert to hex: " << endl;
            cin >> DecNumberSigned;
            convertDecToHex( SignedDecToHex(DecNumberSigned));
        }//3
                if (choice == 4){
            cout << "Enter signed hex to convert to dec: " << endl;
            cin >> HexNumberSigned;
            numberSize = HexNumberSigned.size();
            strcpy(hex, HexNumberSigned.c_str());
             cout << SignedHexToDec(convertHexToDec( hex,  numberSize)) <<     endl;
        }//4
    }//while
    system ("pause");
}//main

 void convertDecToHex(unsigned hexNumber){
int remainder, i=0;
    unsigned m[99999], total, x;
    char n [99999];

    i=0;
    do {
        remainder = hexNumber % 16;
        hexNumber /= 16;
        m[i] = remainder;
        i++;
    }//doLooop
    while (hexNumber > 0);
    total = i;

    for (i=0, x = total - 1; i < total; i++, x--){
        if (m[i] == 1) n[x] = '1';
        if (m[i] == 2) n[x] = '2';
        if (m[i] == 3) n[x] = '3';
        if (m[i] == 4) n[x] = '4';
        if (m[i] == 5) n[x] = '5';
        if (m[i] == 6) n[x] = '6';
        if (m[i] == 7) n[x] = '7';
        if (m[i] == 8) n[x] = '8';
        if (m[i] == 9) n[x] = '9';
        if (m[i] == 10) n[x] = 'A';
        if (m[i] == 11) n[x] = 'B';
        if (m[i] == 12) n[x] = 'C';
        if (m[i] == 13) n[x] = 'D';
        if (m[i] == 14) n[x] = 'E';
        if (m[i] == 15) n[x] = 'F';
    }

    for (i=0; i < total; i++)
        cout << n[i];
    cout << endl;

}//DecToHex
int convertHexToDec(char hex[], unsigned numberSize){
    int i, j;
    int n[10000];
    unsigned sum = 0;
    char a,b,c,d,e,f;

    for (i = 0 ; i < numberSize; i++){
        if (hex[i] == '1') n[i] = 1;
        if (hex[i] == '2') n[i] = 2;
        if (hex[i] == '3') n[i] = 3;
        if (hex[i] == '4') n[i] = 4;
        if (hex[i] == '5') n[i] = 5;
        if (hex[i] == '6') n[i] = 6;
        if (hex[i] == '7') n[i] = 7;
        if (hex[i] == '8') n[i] = 8;
        if (hex[i] == '9') n[i] = 9;
        if (hex[i] == 'a' || hex[i] == 'A') n[i] = 10;
        if (hex[i] == 'b' || hex[i] == 'B') n[i] = 11;
        if (hex[i] == 'c' || hex[i] == 'C') n[i] = 12;
        if (hex[i] == 'd' || hex[i] == 'D') n[i] = 13;
        if (hex[i] == 'e' || hex[i] == 'E') n[i] = 14;
        if (hex[i] == 'f' || hex[i] == 'F') n[i] = 15;

    }//forLoop

    for (i = 0, j = numberSize - 1; i < numberSize , j >= 0 ; i++, j--)
        sum += pow(16,i) * n[j];

    return sum;

}//HexToDec

signed SignedDecToHex (signed DecNumberSigned){
    signed convertNumber;
    convertNumber = DecNumberSigned + (pow (2,16));
    return convertNumber;
 }// SignedDecToHex

 signed SignedHexToDec (int number){
     int newNumber;
    newNumber = number - (pow (2,16));
    return newNumber;

 }//SingedHexToDec

Answer 1

不要使用 pow()在做整数运算时。 pow返回值为 double这是不准确的，并且在将其转换为 int 时可能导致值相差 1 .

理论上，当数字是 2 的幂时，双倍可能是准确的。但这假设您知道自己在做什么，而目前您还不知道 :-)

尽可能使用位移:

pow(2,n) --> 1 << n

如何实现pow(16, n)使用位移位作为练习留给读者。

提示:((i^n)^m) = i ^ (n*m)