10进制和36进制内的互转

R进制转10进制

int to_Dec(int radix, string num) {
    int res = 0;​
    for (char c: num) {
        int val = isdigit(c) ? c - '0' : toupper(c) - 'A' + 10;​
        res = res * radix + val; //R进制转10进制递推公式​
    }​
    return res;​
}

10进制转R进制

string dec_To(int radix, int num) {
    if (num == 0) return "0";​
    string res;​
    while (num) {
        int rema = num % radix;​
        res += (rema < 10) ? ('0' + rema) : ('A' + rema - 10);​
        num /= radix;​
    }​
    reverse(res.begin(), res.end());​
    return res;​
}