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