1. 大整数加法
用数组来存储大整数的每一位, 然后模拟人工运算, 用 for 循环按位运算和处理, 原理十分简单, 直接上模板.
- #include<iostream>
- #include<vector>
- using namespace std;
- // 大整数加法
- 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) C.push_back(1);
- 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');
- auto C = add(A,B);
- for(int i = C.size()-1;i>=0;i--) cout<<C[i];
- cout<<endl;
- return 0;
- }
2. 大整数减法
- #include<iostream>
- #include<vector>
- using namespace std;
- // 判断 A 是否大于等于 B
- 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 1;
- }
- //C = A - B
- 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;
- }
- //C = A + B
- 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) C.push_back(1);
- 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');
- if(cmp(A,B)){
- auto C = sub(A,B);
- for(int i = C.size()-1;i>=0;i--) cout<<C[i];
- cout<<endl;
- }else{
- auto C = sub(B,A);
- cout<<"-";
- for(int i = C.size()-1;i>=0;i--) cout<<C[i];
- cout<<endl;
- }
- return 0;
- }
3. 大整数乘法
- #include <iostream>
- #include <vector>
- using namespace std;
- vector<int> mul(vector<int> A, vector<int> B)
- {
- vector<int> C(A.size() + B.size());
- for (int i = 0; i <A.size(); i ++ )
- for (int j = 0; j < B.size(); j ++ )
- C[i + j] += A[i] * B[j];
- for (int i = 0, t = 0; i < C.size() || t; i ++ )
- {
- t += C[i];
- if (i>= C.size()) C.push_back(t % 10);
- else C[i] = t % 10;
- t /= 10;
- }
- while (C.size()> 1 && !C.back()) 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');
- auto C = mul(A, B);
- for (int i = C.size() - 1; i>= 0; i -- ) cout <<C[i];
- cout << endl;
- return 0;
- }
4. 大整数除法
- #include <iostream>
- #include <vector>
- #include <algorithm>
- using namespace std;
- vector<int> div(vector<int> &A, int b, int &r)
- {
- vector<int> C;
- r = 0;
- for (int i = A.size() - 1; i>= 0; i -- )
- {
- r = r * 10 + A[i];
- C.push_back(r / b);
- r %= b;
- }
- reverse(C.begin(), C.end());
- while (C.size()> 1 && C.back() == 0) C.pop_back();
- return C;
- }
- int main()
- {
- string a;
- vector<int> A;
- int B;
- cin>> a>> B;
- for (int i = a.size() - 1; i>= 0; i -- ) A.push_back(a[i] - '0');
- int r;
- auto C = div(A, B, r);
- for (int i = C.size() - 1; i>= 0; i -- ) cout << C[i];
- cout << endl << r << endl;
- return 0;
- }
来源: http://www.bubuko.com/infodetail-3395612.html