数组高精度
定义：
bignum(){ flag = 1; len = 0; }
赋值运算：
void operator =(long long a) { int i=0; while(a!=0) { N[i]=a%10; a/=10; i++; } len=i;
}
void operator = (string g) { for(int i=0;i<g.size();i++) N[i]=g[g.size()-1-i]-48; len=g.size();
}
输出：
void pt() { if(flag==0) printf("-"); for(int i=len;i>=0;i--) printf("%d",N[i]); }
三则运算：
friend bignum operator + (bignum f,bignum g) { bignum ans; ans.len=max(f.len,g.len)+1; int tp=0; for(int i=0;i<=ans.len;i++) { ans.N[i]=f.N[i]+g.N[i]+tp; tp=ans.N[i]/10; ans.N[i]%=10; } int i=ans.len; while(ans.N[i]==0&&i>0) { ans.len--; i--; } return ans; } friend bignum operator * (bignum f,bignum g) { bignum ans; ans.len=f.len+g.len; int tp=0; for(int i=0;i<f.len;i++) { for(int j=0;j<g.len;j++) { ans.N[i+j]+=f.N[i]*g.N[j]; ans.N[i+j+1]+=ans.N[i+j]/10; ans.N[i+j]%=10; } } int i=ans.len; while(ans.N[i]==0&&i>0) { ans.len--; i--; } return ans; } friend bignum operator - (bignum f,bignum g) { bignum ans; if(f<g) { swap(f,g); ans.flag=0; } ans.len=max(f.len,g.len); for(int i=0;i<f.len;i++) { ans.N[i]=f.N[i]-g.N[i]; if(ans.N[i]<0) { f.N[i+1]--; ans.N[i]+=10; } } int i=ans.len; while(ans.N[i]==0&&i>0) { ans.len--; i--; } return ans; }
比较运算：
friend bool operator < (bignum f,bignum g) { if(f.len<g.len) return true; else if(f.len==g.len) { bool flg=1; for(int i=0;i<g.len;i++)if(f.N[i]<g.N[i]) return true; return false; } else return false; }
完整代码：
1 #include<cstdio> 2 #include<iostream> 3 #include<algorithm> 4 #include<cstring> 5 using namespace std; 6 #define LL long long 7 8 struct bignum { 9 int N[1000],len,flag; 10 11 bignum(){ 12 flag = 1; len = 0; 13 } 14 15 void operator = (LL a) { 16 int i = 0; 17 while(a != 0) { 18 N[i++] = a % 10; 19 a /= 10; 20 } 21 len = i; 22 } 23 24 void operator = (string a) { 25 int lena = a.length(); 26 for(int i = 0;i < lena;i++) N[i] = a[lena-1-i]-'0'; 27 len = lena; 28 } 29 30 friend bignum operator + (bignum a,bignum b) { 31 bignum ret; 32 ret.len = max(a.len,b.len) + 1; 33 int tp = 0; 34 for(int i = 0;i <= ret.len;i++) { 35 ret.N[i] = a.N[i] + b.N[i] + tp; 36 tp = ret.N[i] / 10; 37 ret.N[i] %= 10; 38 } 39 int i = ret.len; 40 while(ret.N[i] == 0 && i > 0) { 41 ret.len--; i--; 42 } 43 return ret; 44 } 45 46 friend bignum operator * (bignum a,bignum b) { 47 bignum ret; 48 ret.len = a.len + b.len; 49 for(int i = 0;i < a.len;i++) { 50 for(int j = 0;j < b.len;j++) { 51 ret.N[i+j] += a.N[i]*b.N[j]; 52 ret.N[i+j+1] += ret.N[i+j]/10; 53 ret.N[i+j] %= 10; 54 } 55 } 56 int i = ret.len; 57 while(ret.N[i] == 0 && i > 0) { 58 ret.len--; i--; 59 } 60 return ret; 61 } 62 63 friend bignum operator - (bignum a, bignum b) { 64 bignum ret; 65 if(a < b) swap(a,b),ret.flag = 0; 66 ret.len = max(a.len, b.len); 67 for(int i = 0;i < a.len;i++) { 68 ret.N[i] = a.N[i] - b.N[i]; 69 if(ret.N[i] < 0) a.N[i+1]--, ret.N[i] += 10; 70 } 71 int i = ret.len; 72 while(ret.N[i] == 0 && i > 0) { 73 ret.len--; i--; 74 } 75 return ret; 76 } 77 78 friend bool operator < (bignum a,bignum b) { 79 if(a.len < b.len) return true; 80 else if(a.len == b.len) { 81 for(int i = 0;i < b.len;i++) if(a.N[i] < b.N[i]) return true; 82 return false; 83 } else return false; 84 } 85 86 void pt() { 87 if(flag == 0) printf("-"); 88 for(int i = len;i >= 0;i--) printf("%d",N[i]); 89 } 90 }; 91 92 int main() { 93 bignum a,b; 94 string aa,bb; 95 cin >> aa >> bb; 96 a = aa; b = bb; 97 (a * b).pt(); 98 return 0; 99 }