高精度减法（模板yxc）

#include <bits/stdc++.h>


using namespace std;









bool cmp(vector<int> &A, vector<int> &B) {
    if (A.size() != B.size()) return A.size() > B.size();
    for (int i = A.size(); i >= 0; i --) {
        if (A[i] != B[i]) return A[i] > B[i];
    }
    return true;  
}









vector<int> sub(vector<int> &A, vector<int> &B) {
    vector<int> C;
    int t = 0;
    for (int i = 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;
}









int main() {
    string a, b;
    vector<int> 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)) {
        auto C = sub(A, B);
        for (int i = C.size() - 1; i >= 0; i --) {
            printf("%d", C[i]);
        }
        return 0;
    }
    else{
        auto C = sub(B, A);
        printf("-");
        for (int i = C.size() - 1; i >= 0; i --) {
            printf("%d", C[i]);
        }
        return 0;
    }
    return 0;
}