高精度乘法

#include<bits/stdc++.h> //万能头文件
using namespace std;

//C = A * B
vector<int> mul(vector<int> &A, int b) {

    vector<int> C;
    int t = 0; //进位

    //为了防止A结束之后t 还有余数
    for (int i = 0; i < A.size() || t; i++) {
        if (i < A.size()) {
            t += A[i] * b;
        }
        C.push_back(t % 10);
        t /= 10;
    }

    return C;
}





int main() {
    //高精度A， 乘以低精度b
    string a;
    int b;

    cin>>a>>b;
    if (b == 0) {
        cout<<0;
        return 0;
    }
    vector<int> A;
    for (int i = a.size() - 1; i >= 0; i--) {
        A.push_back(a[i] - '0');
    }

    auto C = mul(A, b);
    for (int i = C.size() - 1; i >= 0; i--) {
        printf("%d", C[i]);
    }
    return 0;


}