Acwing792.高精度減法

題解

#include <iostream>
#include <vector>
using namespace std;

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> sub(vector<int> &a, vector<int> b)
{
    vector<int> c;
    for(int i = 0, t = 0; i < a.size(); ++i)
    {
        t += a[i];
        if(i < b.size())
            t -= b[i];
        c.push_back( (t + 10)%10 );
        t = t < 0 ? -1 :  0;
    }
    
    while(c.size() > 1 && c.back() == 0) c.pop_back();
    
    return c;
}


int main()
{
    vector<int> A, B;
    string a, b;
    
    cin >> a >> b;
    for(int i = a.size() - 1; i >= 0; --i) A.push_back(a[i] - '0');
    for(int i = b.size() - 1; i >= 0; --i) B.push_back(b[i] - '0');
    
    vector<int> C;
    if(cmp(A, B)) C = sub(A, B);
    else C = sub(B, A), cout << "-";
    
    for(int i = C.size() - 1; i >= 0; --i) cout << C[i];
    cout << endl;
    
    return 0;
}