高精度减法

  

   

    

     

    
    

     

      #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] - 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;
     
    
   

    

     

    
    

     

          vector<int> 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;
     
    
   

    

     

    
    

     

      }
     
    
   

    

     

    
    

     
 
     
    
  
 

  
 
 

直接按位相减sub，同时注意可能产生负数，要做一个大小转化。
 

文章来源: blog.csdn.net，作者：irrationality，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/weixin_54227557/article/details/120595058