高精度

1、加法
vector<int> add(vector<int> &A, vector<int> &B) { if (A.size() < B.size()) { return add(B, A); } vector<int> C;int t = 0;//t作为两个相加的中转处 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; }

2、减法
`bool cmp(vector &A, vector &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 sub(vector &A, vector &B)
{
vector 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 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 << '-';//减法要注意判断被减数，提前输出负号
for (int i = C.size() - 1; i >= 0; i -- ) cout << C[i];
cout << endl;return 0;

}`

3、乘法
vector<int> mul(vector<int> &A, int b) { vector<int> C; int t = 0; for (int i = 0; i < A.size() || t; i ++ ) { if (i < A.size()) {t += A[i] * b;} C.push_back(t % 10); t /= 10; } while (C.size() > 1 && C.back() == 0) C.pop_back(); return C; }

4、除法
`vector div(vector &A, int b, int &r)
{
vector 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 A;
int B;cin >> a >> B;
for (int i = a.size() - 1; i >= 0; i -- ) {A.push_back(a[i] - '0');}

int r;//r是余数
auto C = div(A, B, r);for (int i = C.size() - 1; i >= 0; i -- ) cout << C[i];
cout << endl << r << endl;
return 0;

}`