高精度运算

#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<cstdlib>

using namespace std;
vector<int> A;
vector<int> B;
vector<int> add(vector<int> &A,vector<int> &B)
{
    if(A.size()<B.size())
        return add(B,A);
    vector<int> ans;
    int t = 0,i;
    for(i =0;i<A.size();++i)
    {
        t+=A[i];
        if(i<B.size())
            t+=B[i];
        ans.push_back(t%10);
        t/=10;
    }
    while(i<A.size())
    {
        t += A[i];
        ans.push_back(t%10);
        t /=10;
    }
    if(t)
        ans.push_back(t);
    return  ans;
}
int main()
{
    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');
    auto ans = add(A,B);
    for(int i = ans.size()-1;i>=0;--i)
        cout<<ans[i];
    cout<<endl;
    A.clear();
    B.clear();
    system("pause");
    return 0;
}

#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<cstdlib>

using namespace std;
vector<int> A;
vector<int> B;
bool cmp(vector<int> &A,vector<int> &B){//判断二者数字的大小
    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> Minus(vector<int> &A,vector<int> &B)
{
    vector<int> ans;
    int t = 0,i;
    for(i =0;i<A.size();++i)
    {
        t = A[i]-t;
        if(i<B.size())
            t-=B[i];
        ans.push_back((t+10)%10);
        if(t<0)
            t=1;
        else
            t = 0;
    }
    // while(i<A.size())
    // {
    //     t += A[i];
    //     ans.push_back(t%10);
    //     t /=10;
    // }
    while(ans.size()>1&&ans.back()==0) ans.pop_back();
    return  ans;
}
int main()
{
    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> ans;
    if(cmp(A,B))
        ans = Minus(A,B);
    else
    {
        cout<<'-';
        ans = Minus(B,A);
    }
   
    for(int i = ans.size()-1;i>=0;--i)
        cout<<ans[i];
    cout<<endl;
    A.clear();
    B.clear();
    system("pause");
    return 0;
}

#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<cstdlib>
#include<cstring>
using namespace std;
int A[300],B[300];
int ans[300];

int main()
{
    memset(A,0,sizeof(A));
    memset(B,0,sizeof(B));
    memset(ans,0,sizeof(ans));
    string a,b;
    cin>>a>>b;
    int len1 = a.length(),len2 = b.length();
    for(int i =0;i<len1;++i)
        A[len1-i] = a[i]-'0';
    for(int i = 0;i<len2;++i)
        B[len2-i] = b[i]-'0';
    for(int i =1;i<=len2;++i)
    {
        int x = 0;
        for(int j =1;j<=len1;++j)
        {
            ans[i+j-1] = ans[i+j-1]+A[j]*B[i]+x;
            x = ans[i+j-1]/10;
            ans[i+j-1]%=10;
        }
        ans[i+len1] = x;
    }
    int len = len1+len2;
    while((ans[len]==0)&&(len>1))
    {
        len--;
    }
    for(int i = len;i>0;--i)
        cout<<ans[i];
    cout<<endl;
   
    system("pause");
    return 0;
}