[AcWing 793] 高精度乘法

---

点击查看代码

#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;
}

---

1. i < A.size( ) | | t 设置的很巧妙；
2. 123 × 0 用模板计算后会是 000，所以记得去掉前导的 0；