addition
#include<bits/stdc++.h>
using namespace std;
vector<int> add(vector<int> A,vector<int> B){
vector<int> C;
if(B.size()>A.size()) return add(B,A);
else{
int t=0;
for(int i=0;i<A.size();i++)
{
t+=A[i];
if(i<B.size()) t+=B[i];
C.push_back(t%10);
t/=10;
}
//容易忘记————最高位进1
if(t) C.push_back(t);
return C;
}
}
int main(){
string a,b;
vector<int> A,B;
cin>>a>>b;
//读数拆分(高位拆分)
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=add(A,B);
for(int i=C.size()-1;i>=0;i--)
cout<<C[i];
}
subtraction
#include<bits/stdc++.h>
using namespace std;
//判断A>=B
bool cmp(vector<int> A,vector<int> B){
if(A.size()!=B.size()) return A.size()>B.size();
else{
for(int i=A.size()-1;i>=0;i--){
if(A[i]!=B[i])
return A[i]>B[i];
}
}
//容易忘记返回1
return 1;
}
vector<int> sub(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;
}
int main(){
string a,b;
cin>>a>>b;
vector<int> A,B;
//高位读入
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);
for(int i=C.size()-1;i>=0;i--){
cout<<C[i];
}
}else{
cout<<"-";
C=sub(B,A);
for(int i=C.size()-1;i>=0;i--){
cout<<C[i];
}
}
}
multiplication
#include<bits/stdc++.h>
using namespace std;
vector<int> mul(vector<int> &A,int b){
vector<int> C;
int t=0;
for(int i=0;i<A.size();i++){
t+=A[i]*b;
C.push_back(t%10);
t/=10;
}
//最高位进位
if(t) C.push_back(t);
//去掉先导0
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--)
cout<<C[i];
}
division
#include<bits/stdc++.h>
using namespace std;
vector<int> div(vector<int> &A,int b,int &r){
vector<int> C;
for(int i=A.size()-1;i>=0;i--){
r=r*10+A[i];
C.push_back(r/b);
r%=b;
}
//不翻转去不掉前导0;
reverse(C.begin(),C.end());
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');
//r为余数
int r=0;
auto C=div(A,b,r);
for(int i=C.size()-1;i>=0;i--) cout<<C[i];
cout<<endl<<r;
}