真没人用高精度吗？

1. 高精度

#include <bits/stdc++.h>
using namespace std;
struct BigInt {
    string num;
    bool isNeg;
    BigInt(string s = "0") {
        if(s[0] == '-') {
            isNeg = true;
            num = s.substr(1);
        } else {
            isNeg = false;
            num = s;
        }
        num = removeLeadingZeros(num);
        if(num == "0") isNeg = false;
    }
    string toString() const {
        return (isNeg ? "-" : "") + num;
    }
    static string removeLeadingZeros(string s) {
        int i = 0;
        while(i < s.size()-1 && s[i] == '0') i++;
        return s.substr(i);
    }
};
int compare(string a, string b) {
    a = BigInt::removeLeadingZeros(a);
    b = BigInt::removeLeadingZeros(b);
    if(a.size() != b.size()) 
        return a.size() > b.size() ? 1 : -1;
    return a.compare(b);
}
string add(string a, string b) {
    string res;
    int carry = 0;
    int i = a.size()-1, j = b.size()-1;
    while(i >= 0 || j >= 0 || carry) {
        int sum = carry;
        if(i >= 0) sum += a[i--]-'0';
        if(j >= 0) sum += b[j--]-'0';
        carry = sum / 10;
        res += (sum % 10) + '0';
    }
    reverse(res.begin(), res.end());
    return BigInt::removeLeadingZeros(res);
}
string sub(string a, string b) {
    string res;
    int borrow = 0;
    int i = a.size()-1, j = b.size()-1;
    while(i >= 0) {
        int x = a[i--]-'0' - borrow;
        int y = j >= 0 ? b[j--]-'0' : 0;
        borrow = 0;
        if(x < y) {
            x += 10;
            borrow = 1;
        }
        res += (x - y) + '0';
    }
    reverse(res.begin(), res.end());
    return BigInt::removeLeadingZeros(res);
}
string mul(string a, string b) {
    if(a == "0" || b == "0") return "0";
    int m = a.size(), n = b.size();
    vector<int> res(m+n, 0);
    for(int i = m-1; i >= 0; i--) {
        for(int j = n-1; j >= 0; j--) {
            int product = (a[i]-'0') * (b[j]-'0');
            int sum = product + res[i+j+1];
            res[i+j+1] = sum % 10;
            res[i+j] += sum / 10;
        }
    }
    string ans;
    for(int num : res) {
        if(!ans.empty() || num != 0) {
            ans += to_string(num);
        }
    }
    return ans;
}
pair<string, string> divide(string a, string b) {
    if(b == "0") return {"0", "0"};
    string quotient;
    string remainder;
    for(int i = 0; i < a.size(); i++) {
        remainder += a[i];
        remainder = BigInt::removeLeadingZeros(remainder);
        int count = 0;
        while(compare(remainder, b) >= 0) {
            remainder = sub(remainder, b);
            count++;
        }
        quotient += to_string(count);
    }
    quotient = BigInt::removeLeadingZeros(quotient);
    remainder = BigInt::removeLeadingZeros(remainder);
    if(quotient.empty()) quotient = "0";
    if(remainder.empty()) remainder = "0";
    return {quotient, remainder};
}
void solve(BigInt A, BigInt B) {
    string sum;
    if(A.isNeg == B.isNeg) {
        sum = add(A.num, B.num);
        if(A.isNeg) sum = "-" + sum;
    } else {
        int cmp = compare(A.num, B.num);
        if(cmp == 1) {
            sum = sub(A.num, B.num);
            if(A.isNeg && sum != "0") sum = "-" + sum;
        } else if(cmp == -1) {
            sum = sub(B.num, A.num);
            if(B.isNeg && sum != "0") sum = "-" + sum;
        } else {
            sum = "0";
        }
    }
    cout << sum << endl;
    string diff;
    if(A.isNeg != B.isNeg) {
        diff = add(A.num, B.num);
        if(A.isNeg) diff = "-" + diff;
    } else {
        int cmp = compare(A.num, B.num);
        if(cmp == 1) {
            diff = sub(A.num, B.num);
            if(A.isNeg && diff != "0") diff = "-" + diff;
        } else if(cmp == -1) {
            diff = sub(B.num, A.num);
            if(!A.isNeg && diff != "0") diff = "-" + diff;
        } else {
            diff = "0";
        }
    }
    cout << diff << endl;
    string product = mul(A.num, B.num);
    if(A.isNeg != B.isNeg && product != "0") {
        product = "-" + product;
    }
    cout << product << endl;
    auto [quotient, remainder] = divide(A.num, B.num);
    if(A.isNeg != B.isNeg && quotient != "0") {
        quotient = "-" + quotient;
    }
    cout << quotient << endl;
    if(A.isNeg && remainder != "0") {
        remainder = "-" + remainder;
    }
    cout << remainder << endl;
}
int main() {
    string s1, s2;
    cin >> s1 >> s2;
    BigInt A(s1), B(s2);
    solve(A, B);
    return 0;
}

2. 普解：

#include <bits/stdc++.h>
using namespace std;
int main() {
    short a,b;
    cin>>a>>b;
    cout<<a+b<<endl<<a-b<<endl<<a*b<<endl<<a/b<<endl<<a%b;
    return 0;
}