《高精度减法》

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<int> A, B, C;
bool cmp(vector<int> &A, vector<int> &B)
{
    if (A.size() != B.size()) return A.size() > B.size();
    else
    {
        for (int i = A.size() - 1; i >= 0; i --)
        {
            if (A[i] != B[i])
            {
                return A[i] > B[i];
            }
        }
    }
    return true;
}
vector<int> sub(vector<int> &A, vector<int> &B)
{
    for (int i = 0, t = 0; i < A.size(); i ++)
    {
        t = A[i] - t;
        if (i < B.size()) t -= B[i];
        C.push_back((t + 10) % 10);
        if (t < 0) t = 1;
        else t = 0;
    }
    while (C.size() > 1 && C.back() == 0) C.pop_back();
    return C;
}
void solve()
{
    string a, b;
    cin >> a >> b;
    for (int i = a.size() - 1; i >= 0; i --) A.push_back(a[i] - '0');
    for (int i = b.size() - 1; i >= 0; i --) B.push_back(b[i] - '0');
    if (cmp(A, B))
    {
        C = sub(A, B);
    }
    else
    {
        C = sub(B, A);
        cout << '-';
    }
    for (int i = C.size() - 1; i >= 0; i --) cout << C[i];
    A.clear(), B.clear(), C.clear();
    cout << endl; 
}
int main()
{
    int t;
    cin >> t;
    while (t --)
    {
        solve();
    }
    return 0;
}