C++ 代码

#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;
    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;
    }
    while(C.size()>1&&C.back()==0)C.pop_back();
    return C;
}

int main(){
    string a,b;
    cin>>a>>b;
    vector<int>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;
}