十进制转为二进制

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>

using namespace std;
const int N = 1000;
int n, num;
int a[N];

int main(){
    cin >> n;
    do{  //不用while循环,可以有效处理n == 0的情况
        a[num ++] = n % 2;
        n /= 2;
    }while(n != 0);

    for(int i = num - 1; i >= 0; i --){
        cout << a[i];
    }

    return 0;
}

十进制转为十六进制

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>

using namespace std;
const int N = 1000;
int n, num;
int a[N];
char h[17] = {'0', '1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};//十六进制

int main(){
    cin >> n;
    do{  //不用while循环,可以有效处理n == 0的情况
        a[num ++] = n % 16;
        n /= 16;
    }while(n != 0);

    for(int i = num - 1; i >= 0; i --){
        int n = a[i];
        cout << h[n];
    }

    return 0;
}