题解 | #进制转换#

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

int main() {
    string hex;
    cin >> hex;
    
    // 去掉"0x"前缀
    hex = hex.substr(2);
    
    // 将十六进制转换为十进制
    int decimal = 0;
    for(char c : hex) {
        decimal *= 16;
        if(c >= '0' && c <= '9') {
            decimal += c - '0';
        } else {
            decimal += (toupper(c) - 'A' + 10);
        }
    }
    
    cout << decimal << endl;
    return 0;
}

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String hex = sc.nextLine();
        
        // 方法1：使用Integer内置方法
        System.out.println(Integer.parseInt(hex.substring(2), 16));
        
        /* 方法2：手动实现
        hex = hex.substring(2);  // 去掉0x
        int decimal = 0;
        for(char c : hex.toCharArray()) {
            decimal = decimal * 16 + 
                     (Character.isDigit(c) ? c - '0' : Character.toUpperCase(c) - 'A' + 10);
        }
        System.out.println(decimal);
        */
    }
}

# 读取输入，去掉0x前缀
hex_str = input().strip()[2:]

# 方法1：使用int内置函数
print(int(hex_str, 16))

'''
# 方法2：手动实现
decimal = 0
for c in hex_str:
    decimal *= 16
    if c.isdigit():
        decimal += int(c)
    else:
        decimal += ord(c.upper()) - ord('A') + 10
print(decimal)
'''