题解 | #Powerful Calculator#
Powerful Calculator
http://www.nowcoder.com/practice/6bc1dd2ee0ce4257821531719b8d1c83
#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
using namespace std;
void print(vector<int> &A)
{
for(int i = A.size() - 1; i >= 0; i--)
printf("%d", A[i]);
printf("\n");
}
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> add(vector<int> &A, vector<int> &B)
{
vector<int> res;
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];
res.push_back(t % 10);
t /= 10;
}
if(t) res.push_back(1);
return res;
}
// A > B -> A - B
vector<int> sub(vector<int> &A, vector<int> &B)
{
vector<int> res;
int t = 0;
for(int i = 0; i < A.size(); i ++)
{
t = A[i] - t;
if(i < B.size()) t = t - B[i];
res.push_back((t + 10) % 10);
if(t < 0) t = 1;
else t = 0;
}
while(res.size() > 1 && res.back() == 0) res.pop_back();
return res;
}
vector<int> mul(vector<int> &A, vector<int> &B)
{
int m = A.size(), n = B.size();
int carry = 0, tmp;
vector<int> ans(m + n, 0); //初始化为0
ans.push_back(0);
for(int i = 0; i < m; i++){
for(int j = 0; j < n; j++){
ans[i + j] += A[i] * B[j];
}
}
for(int i = 0; i < m + n + 2; i++){
if(ans[i] > 10){
ans[i+1] += ans[i] / 10;
ans[i] = ans[i] % 10;
}
}
while(ans.size() > 1 && ans.back() == 0) ans.pop_back();
return ans;
}
int main()
{
string a;
string b;
vector<int> A;
vector<int> B;
while(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> add_ans = add(A, B);
print(add_ans);
vector<int> sub_ans;
if(cmp(A, B)) sub_ans = sub(A, B);
else
{
sub_ans = sub(B, A);
printf("-");
}
print(sub_ans);
vector<int> mul_ans;
if(cmp(A, B)) mul_ans = mul(A, B);
else mul_ans = mul(B, A);
print(mul_ans);
}
return 0;
}