C++大数模板 BigInteger

网上搜集的一份写的灰常漂亮的大数模板。Mark之~~~~

看不懂的自行补脑了 +_+

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;

struct BigInteger{
int A[25];
enum{MOD = 10000};
BigInteger(){memset(A, 0, sizeof(A)); A[0]=1;}
void set(int x){memset(A, 0, sizeof(A)); A[0]=1; A[1]=x;}
void print(){
printf("%d", A[A[0]]);
for (int i=A[0]-1; i>0; i--){
if (A[i]==0){printf("0000"); continue;}
for (int k=10; k*A[i]<MOD; k*=10) printf("0");
printf("%d", A[i]);
}
printf("\n");
}
int& operator [] (int p) {return A[p];}
const int& operator [] (int p) const {return A[p];}
BigInteger operator + (const BigInteger& B){
BigInteger C;
C[0]=max(A[0], B[0]);
for (int i=1; i<=C[0]; i++)
C[i]+=A[i]+B[i], C[i+1]+=C[i]/MOD, C[i]%=MOD;
if (C[C[0]+1] > 0) C[0]++;
return C;
}
BigInteger operator * (const BigInteger& B){
BigInteger C;
C[0]=A[0]+B[0];
for (int i=1; i<=A[0]; i++)
for (int j=1; j<=B[0]; j++){
C[i+j-1]+=A[i]*B[j], C[i+j]+=C[i+j-1]/MOD, C[i+j-1]%=MOD;
}
if (C[C[0]] == 0) C[0]--;
return C;
}
};
int main() {
BigInteger a, b;
a.set(1); b.set(1);
(a+b).print();

return 0;
}