蓝桥杯训练——基础练习 十六进制转八进制

》》原题传送门《《

思路：本来想偷懒直接调用，C语言自带的进制转化函数，但是交了一发之后才发现这个数太太太太大了；所以还不能先转化为十进制，当然如果你愿意用数组存的话，蛮难搞的。这个题目就是先转化成二进制用数组存，十六进制转二进制，一位转四位，二进制转八进制，三位转一位；注意前导零，注意细节不然就会像我一样发现自己傻不啦叽。

#include<cstdio>
#include<stack>
#include<string>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
int a[500005], b[500010];
int rnum(char ch){
    if (ch >= '0'&&ch <= '9')
        return ch - '0';
    if (ch >= 'A'&&ch <= 'F')
        return ch - 'A' + 10;
}
int main(){

    
    int n; cin >> n;
    int ta[10];
    getchar();
    char cnt;
    while (n--){
        int len = 0;
        while ((cnt = getchar()) != '
'){
            int num = rnum(cnt);
            int ans = 0;
            //cout <<"num = "<< num << endl;
            while (num > 0){
                b[len++] = num % 2;
                num /= 2;
                ans++;
            }
            //cout << "ans = " << ans << endl;
            for (; ans < 4; ans++)
                b[len++] = 0;
            for (int i = len - 4, j = 0; i < len; i++, j++){
                ta[j] = b[i];
            }
            for (int i = len - 4, j = 3; i < len; i++, j--){
                b[i] = ta[j];
            }
        }
        /*for (int i = 0; i < len; i++){
            cout << b[i];
            if (i % 4 == 3)cout << " ";
        }
        cout << " len = " << len << endl;
        cout << endl;*/
        int ocn = len / 3;
        if (len % 3 == 0) ocn -= 1; 
        int len_a = 0, i, j, temp;
        for (i = len - 1, j = 0; j < ocn; j++){
            temp = b[i--];
            temp += b[i--] * 2;
            temp += b[i--] * 4;
            //cout << "temp = " << temp <<" "<< i << endl;
            a[len_a++] = temp;
        }
        
        temp = 0;
        if (i >= 0)temp = b[i--];
        if (i >= 0)temp += b[i--] * 2;
        if (i >= 0)temp += b[i--] * 4;
        if (temp > 0)a[len_a++] = temp;

        for (int i = len_a - 1; i >= 0; i--){
            if (i == len_a - 1 && a[i] == 0)continue;
            cout << a[i];
        }
        cout << endl;
        //cout << a << endl;
        //long int num = strtol(a, &b, 16);
        //itoa(num, c, 8);
        //cout << std::oct << num << endl;
        //cout << b << endl;
    }
    
    return 0;
}