高精度乘法

Posted by 磊落 on May 11, 2020

高精度乘法

特点

思想

  • 模拟乘法
#include <iostream>
#include <algorithm>

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;
    }
    
    // 剔除前导零
    while (C.back() == 0 && C.size() > 1) 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;
}