高精度乘法

 1 #include <iostream>
 2 #include <vector>
 3 using namespace std;
 4 
 5 vector<int> mul(vector<int>& A, int &b)
 6 {
 7     vector<int> C;
 8     int t = 0;
 9     for (int i = 0; i < A.size() || t; i++)
10     {
11         if (i < A.size()) t += A[i] * b;
12         C.push_back(t % 10);
13         t /= 10;
14     }
15     while(C.size()>1&&C.back() == 0) C.pop_back();
16     return C;
17 }
18 
19 int main()
20 {
21     string a;
22     int b;
23     cin >> a >> b;
24     vector<int> A;
25     for (int i = a.size() - 1; i >= 0; i--) A.push_back(a[i] - '0');
26     auto C = mul(A, b);
27     for (int i = C.size() - 1; i >= 0; i--) cout << C[i];
28     return 0;
29 }