C++高精度运算

1. 高精度加法

vector<int> add(vector<int> &A, vector<int> &B)
{
    vector<int> C;
    int t = 0;
    
    for(int i = 0; i < A.size() || i < B.size(); i++)
    {
        if(i < A.size()) t += A[i];
        if(i < B.size()) t += B[i];
        C.push_back(t % 10);
        t /= 10;
    }
    
    if(t) C.push_back(1);
    return C;
}

2. 高精度减法

//判断A B 的大小， 保证函数里面是大的减小的
bool cmp(vector<int> &A, vector<int> &B)
{
    if(A.size() != B.size()) return A.size() > B.size();
    
    for(int i = A.size() - 1; i >= 0; i--)
        if(A[i] != B[i]) return A[i] > B[i];
    
    return true;
    
}
vector<int> add(vector<int> &A, vector<int> &B)
{
    vector<int> C;
    int t = 0;
    
    for(int i = 0; i < A.size() ; i++)
    {
        t = A[i] - t;
        if(i < B.size()) t = t - B[i];
        C.push_back((t + 10) % 10);
        if(t < 0) t = 1;
        else t = 0;
    }
    
    while(C.size() > 1 && C.back() == 0) C.pop_back();
    return C;
}

3.高精度乘低精度

vector<int> mul(vector<int> &A, int b)
{
    vector<int> C;
    int t = 0;
   for(int i = 0; i < A.size(); i++){
       t += b * A[i];
       C.push_back(t % 10);
       t /= 10;
   } 
   if(t) C.push_back(t);
    return C;
}

4.高精度除低精度

A除b余r
vector<int> div(vector<int> &A, int b, int &r)
{
    vector<int> C;
    int t = 0;
    for(int i = A.size() - 1; i >= 0; i--){
        t *= 10;
        t += A[i];
        C.push_back(t / b);
        t %= b;
    }
    r = t;
    reverse(C.begin(), C.end());
    while(C.size() > 1 && C.back() == 0) C.pop_back();
 
    return C;
}