怎样用C++编写进制转换工具 不同进制间的转换算法

#include <string>
#include <algorithm> // for std::reverse
#include <iostream>  // for example usage

// 辅助函数：将数字0-35转换为对应的字符
char toChar(int digit) {
    if (digit >= 0 && digit <= 9) {
        return static_cast<char>('0' + digit);
    } else if (digit >= 10 && digit <= 35) {
        return static_cast<char>('A' + (digit - 10));
    }
    // 理论上不会到这里，除非输入错误
    return ' ';
}

// 十进制转任意进制 (2-36)
std::string decimalToNBase(long long decimalNum, int base) {
    if (base < 2 || base > 36) {
        return "Error: Base must be between 2 and 36.";
    }
    if (decimalNum == 0) {
        return "0"; // 0在任何进制都是0
    }

    std::string result = "";
    bool isNegative = false;
    if (decimalNum < 0) {
        isNegative = true;
        decimalNum = -decimalNum; // 转换为正数进行处理
    }

    while (decimalNum > 0) {
        int remainder = decimalNum % base;
        result += toChar(remainder); // 将余数转换为字符并添加到结果字符串
        decimalNum /= base;
    }

    if (isNegative) {
        result += '-'; // 如果是负数，添加负号
    }

    std::reverse(result.begin(), result.end()); // 核心：字符串反转
    return result;
}

/*
// 示例用法
int main() {
    std::cout << "10 (Decimal) to Binary: " << decimalToNBase(10, 2) << std::endl; // Output: 1010
    std::cout << "255 (Decimal) to Hex: " << decimalToNBase(255, 16) << std::endl; // Output: FF
    std::cout << "100 (Decimal) to Base 7: " << decimalToNBase(100, 7) << std::endl; // Output: 202
    std::cout << "-42 (Decimal) to Base 13: " << decimalToNBase(-42, 13) << std::endl; // Output: -33
    return 0;
}
*/

#include <string>
#include <cmath>     // for std::pow, though for integers it's often better to multiply manually
#include <algorithm> // for std::reverse (if you iterate from end, not strictly needed)
#include <iostream>  // for example usage

// 辅助函数：将字符转换为对应的数字0-35
int toDigit(char c) {
    if (c >= '0' && c <= '9') {
        return c - '0';
    } else if (c >= 'A' && c <= 'Z') { // 大写字母
        return c - 'A' + 10;
    } else if (c >= 'a' && c <= 'z') { // 小写字母 (为了兼容性，通常只用大写或统一转换)
        return c - 'a' + 10;
    }
    return -1; // 无效字符
}

// 任意进制 (2-36) 转十进制
long long nBaseToDecimal(const std::string& nBaseNum, int base) {
    if (base < 2 || base > 36) {
        return -1; // 错误码，表示基数无效
    }

    long long decimalNum = 0;
    long long power = 1; // 对应当前位的权值，从 base^0 开始

    // 检查并处理负号
    std::string numStr = nBaseNum;
    bool isNegative = false;
    if (!numStr.empty() && numStr[0] == '-') {
        isNegative = true;
        numStr = numStr.substr(1); // 移除负号
    }

    // 遍历字符串，从右到左（低位到高位）
    for (int i = numStr.length() - 1; i >= 0; --i) {
        char c = numStr[i];
        int digit = toDigit(c);

        if (digit == -1 || digit >= base) {
            // 无效字符或字符值超出当前进制范围
            return -1; // 错误码
        }

        decimalNum += digit * power;
        // 检查溢出，虽然这里用long long，但仍是个好习惯
        if (power > LLONG_MAX / base && i > 0) { // 简单检查，防止power溢出
            return -2; // 溢出错误码
        }
        power *= base; // 权值增加
    }

    return isNegative ? -decimalNum : decimalNum;
}

/*
// 示例用法
#include <limits> // For LLONG_MAX
int main() {
    std::cout << "1010 (Binary) to Decimal: " << nBaseToDecimal("1010", 2) << std::endl; // Output: 10
    std::cout << "FF (Hex) to Decimal: " << nBaseToDecimal("FF", 16) << std::endl;     // Output: 255
    std::cout << "202 (Base 7) to Decimal: " << nBaseToDecimal("202", 7) << std::endl; // Output: 100
    std::cout << "-33 (Base 13) to Decimal: " << nBaseToDecimal("-33", 13) << std::endl; // Output: -42
    std::cout << "Invalid base (1): " << nBaseToDecimal("10", 1) << std::endl; // Output: -1
    std::cout << "Invalid digit (2 in binary): " << nBaseToDecimal("102", 2) << std::endl; // Output: -1
    return 0;
}
*/

// 完整的进制转换函数
std::string convertBase(const std::string& numStr, int sourceBase, int targetBase) {
    if (sourceBase < 2 || sourceBase > 36 || targetBase < 2 || targetBase > 36) {
        return "Error: Bases must be between 2 and 36.";
    }

    // 1. 将源进制数转换为十进制
    long long decimalVal = nBaseToDecimal(numStr, sourceBase);
    if (decimalVal == -1) {
        return "Error: Invalid number format for source base.";
    }
    if (decimalVal == -2) {
        return "Error: Number too large (overflow).";
    }

    // 2. 将十进制数转换为目标进制
    return decimalToNBase(decimalVal, targetBase);
}

/*
// 示例用法
int main() {
    std::cout << "1010 (Binary) to Hex: " << convertBase("1010", 2, 16) << std::endl; // Output: A
    std::cout << "FF (Hex) to Binary: " << convertBase("FF", 16, 2) << std::endl;     // Output: 11111111
    std::cout << "123 (Decimal) to Base 5: " << convertBase("123", 10, 5) << std::endl; // Output: 443
    std::cout << "Invalid input (G in Base 10): " << convertBase("10G", 10, 2) << std::endl; // Output: Error: Invalid number format for source base.
    return 0;
}
*/