// C = A + B, A >= 0, B >= 0
vector<int>add(vector<int>&A, vector<int>&B){if(A.size()< B.size())returnadd(B, A);
vector<int> C;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;}if(t) C.push_back(t);return C;}
高精度減法
// C = A - B, 滿足A >= B, A >= 0, B >= 0
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;}