Posted on 2008-09-03 19:14
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代碼如詩－－ACM
1 //2389 Accepted 452K 0MS G++ 2363B PKU
2
3 //高精度乘法
4 #include <iostream>
5 using namespace std;
6
7 const int Base=1000000000;
8 const int Dlen=300;
9 typedef long long llong;
10 struct BigInt{
11 int Len;
12 int Data[Dlen];
13 BigInt():Len(0){}
14 BigInt(const BigInt &num):Len(num.Len){memcpy(Data,num.Data,Len*sizeof*Data);}
15 BigInt(int num):Len(0){for(;num>0;num/=Base) Data[Len++]=num%Base;}
16 BigInt &operator=(const BigInt &num){Len=num.Len;memcpy(Data,num.Data,Len*sizeof*Data);return *this;}
17 int &operator[](int Index){return Data[Index];}
18 int operator[](int Index)const{return Data[Index];}
19 };
20 int compare(const BigInt &A,const BigInt &B){
21 if(A.Len!=B.Len) return A.Len>B.Len ? 1:-1;
22 int i;
23 for(i=A.Len-1;i>=0 && A[i]==B[i];i--);
24 if(i<0)return 0;
25 return A[i]>B[i] ? 1:-1;
26 }
27 BigInt operator+(const BigInt &A,const BigInt &B){
28 int i,Carry(0);
29 BigInt R;
30 for(i=0;i<A.Len||i<B.Len||Carry>0;i++){
31 if(i<A.Len) Carry+=A[i];
32 if(i<B.Len) Carry+=B[i];;
33 R[i]=Carry%Base;
34 Carry/=Base;
35 }
36 R.Len=i;
37 return R;
38 }
39 BigInt operator-(const BigInt &A,const BigInt &B){
40 int i,Carry(0);
41 BigInt R;
42 R.Len=A.Len;
43 for(i=0;i<R.Len;i++){
44 R[i]=A[i]-Carry;
45 if(i<B.Len) R[i]-=B[i];
46 if(R[i]<0) Carry=1,R[i]+=Base;
47 else Carry=0;
48 }
49 while(R.Len>0&&R[R.Len-1]==0) R.Len--;
50 return R;
51 }
52 BigInt operator*(const BigInt &A,const int &B){
53 int i;
54 llong Carry(0);
55 BigInt R;
56 for(i=0;i<A.Len||Carry>0;i++){
57 if(i<A.Len) Carry+=llong(A[i])*B;
58 R[i]=Carry%Base;
59 Carry/=Base;
60 }
61 R.Len=i;
62 return R;
63 }
64 istream &operator>>(istream &In,BigInt &num){
65 char Ch;
66 for(num=0;In>>Ch;){
67 num=num*10+(Ch-'0');
68 if(In.peek()<=' ') break;
69 }
70 return In;
71 }
72 ostream &operator<<(ostream &Out,const BigInt &num){
73 int i;
74 Out<<(num.Len==0 ? 0:num[num.Len-1]);
75 for(i=num.Len-2;i>=0;i--) for(int j=Base/10;j>0;j/=10) Out<<num[i]/j%10;
76 return Out;
77 }
78
79 BigInt Bint0(0) ;
80 BigInt Bint1(1) ;
81
82 BigInt ina, inb, inc ;
83 BigInt out ;
84
85 int main()
86 {
87 while( cin >> ina >> inb )
88 {
89 inc = Bint1 ; out = Bint0 ;
90 for( int i=0; i<inb.Len; i++ )
91 {
92 inc = ina * inb.Data[i] ;
93 for( int j=0; j<i; j++ ) inc = inc * Base ;
94 out = out + inc ;
95 }
96
97
98 cout << out << endl ;
99 }
100
101 return 0 ;
102 }