[AcWing 793] 高精度乘法

#include<iostream> #include<vector>  using namespace std;  vector<int> mul(vector<int>& A, int b) {     vector<int> C;     int t = 0;     for (int i = 0; i < A.size() || t; i++) {         if (i < A.size())   t += A[i] * b;         C.push_back(t % 10);         t /= 10;     }     while (C.size() > 1 && C.back() == 0)   C.pop_back();     return C; } int main() {     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 --) printf(%d, C[i]);     return 0; }