Foreword
Two days in the brush algorithm problem, which involves a high-precision arithmetic, since I use C ++, so it is necessary to manually Simulation. Using java and python students can not worry, Java has a BigDecimal class can implement, python can be implemented directly.
Well, let's directly on the code, the code has a corresponding comment, I believe you can read it.
Code
#include <iostream>
#include <vector>
#include <cstdio>
using namespace std;
//比较两个数的大小
bool checkSize(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 true;
break;
}
if(A[i]<B[i])
{
return false;
break;
}
}
return true;
}
//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!=0) C.push_back(1);
return C;
}
//减法
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-=B[i];
C.push_back((t+10)%10);
if(t<0) t=1;
else t=0;
}
//去除前导0
while(C.size()>1 && C.back()==0) C.pop_back();
return C;
}
int main()
{
string a,b,op;
vector<int> A,B;
cin >> a >> op >>b;
for(int i=a.size()-1;i>=0;i--) A.push_back(a[i]-'0');//将字符转成数字并存进数组中
for(int i=b.size()-1;i>=0;i--) B.push_back(b[i]-'0');
if(op=="add")
{
vector<int> C = add(A,B);
for(int i=C.size()-1;i>=0;i--) printf("%d",C[i]);
}
if(op=="sub")
{
vector<int> C;
if(checkSize(A,B))
{
C= sub(A,B);
for(int i=C.size()-1;i>=0;i--) printf("%d",C[i]);
}
else
{
C = sub(B,A);
cout << "-";
for(int i=C.size()-1;i>=0;i--) printf("%d",C[i]);
}
}
return 0;
}