代码
//
// Created by Genes on 2020/11/29.
//
// 高精度乘法
#include <iostream>
#include <vector>
#define ios \
ios::sync_with_stdio(false); \
cin.tie(nullptr); \
cout.tie(nullptr)
using namespace std;
vector<int> mul(vector<int> &A, int b) {
vector<int> C;
int t = 0; //第0位的进位是0(没有
for (int i = 0; i < A.size() || t; i++) { //只有A还有或者t不为0, 就做, 最后t是不会剩下的
if (i < A.size()) {
t += A[i] * b;
}
C.push_back(t % 10);
t /= 10;
}
// if(t){
// C.push_back(t);
// }
while (C.size() > 1 && C.back() == 0) {
C.pop_back();
}
return C;
}
int main() {
ios;
string a;
int b;
cin >> a >> b;
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--) {
cout << C[i];
}
cout << endl;
return 0;
}