算法模板（1）——高精度

#include<cstdio>
#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
const int MR=1e3+2;

struct Big{
	int l;
	int num[MR];
	void set(string s){
		//用s设置l与num[]的值
		l = s.size();
    	for (int i = 1;i <= l;i++) num[i] = s[l - i] - '0';
	}
	void set(int x){
		set(to_string(x));
	}
	void print(){
		for(int i = l;i >= 1;i--){
			cout <<num[i];
		}
	}
};

bool operator<(Big x,Big y){
	if(x.l!=y.l) return x.l<y.l;
	for(int i = x.l;i >= 1;i--){
		if(x.num[i]!=y.num[i]) return x.num[i]<y.num[i];
	}
	return 0;
}

Big operator+(Big a,Big b){
	Big c;
	int al=a.l,bl=b.l;
	int cl=max(al,bl);
	int u=0;
    for (int i = 1;i <= cl;i++) {
    	if(i<=al) u+=a.num[i];
    	if(i<=bl) u+=b.num[i];
    	c.num[i]=u%10;
    	u/=10;
    }
    if(u>0){
    	cl++;
    	c.num[cl]=u;
    }
    c.l=cl;
    return c;
}

Big operator-(Big a,Big b){
	Big c;
	c.l=a.l;
	int u=0;
	for (int i = 1;i <= c.l;i++) {
    	u+=a.num[i];
    	if(i<=b.l) u-=b.num[i];
    	
    	if(u<0){
    		c.num[i]=u+10;
    		u=-1;
    	}
    	else{
    		c.num[i]=u;
    		u=0;
    	}
	}
	while(c.l>1&&c.num[c.l]==0) c.l--;
	return c;
}

Big operator*(Big a,int b){
	Big c;
	int al=a.l;
	c.l=al;
	long long u=0;
	for(int i = 1;i <= c.l;i++){
		u+=1ll*a.num[i]*b;
		c.num[i]=u%10;
		u/=10;
	}
	while(u>0){
		c.l++;
		c.num[c.l]=u%10;
		u/=10;
	}
	return c;
}

Big operator/(Big a,int b){
	Big c;
	c.l=a.l;
	long long r=0;
	for(int i = c.l;i >= 1;i--){
		r=r*10+a.num[i];
		c.num[i]=r/b;
		r%=b;
	}
	while(c.num[c.l]==0&&c.l>1) c.l--;
	return c;
}
int main(){
	char x;
	string a;
	Big A,B;
	
	cin >> x >> a;
	A.set(a);
	if(x=='+'){
		string b;
		cin >> b;
		B.set(b);
		A=A+B;
		A.print();
	}
	else if(x=='-'){
		string b;
		cin >> b;
		Big B,C;
		B.set(b);
		if(A<B) C=B-A;
		else C=A-B;
		C.print();
	}
	else if(x=='*'){
		int b;
		cin >>  b;
		A=A*b;
		A.print();
	}
	else if(x=='/'){
		int b;
		cin >> b;
		A=A/b;
		A.print();
	}
	return 0;
}

/*
高精乘高精：
for(int i =1 ;i<=al;i++)
	for(int j = 1;j <= bl;j++)
		c.num[i+j-1]+=a[i]*b[j];
*/