大数模板

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

const int numlen = 205; // 位数

int max(int a, int b) { return a>b?a:b; }
struct bign {
int len, s[numlen];
bign() {
memset(s, 0, sizeof(s));
len = 1;
}
bign(int num) { *this = num; }
bign(const char *num) { *this = num; }
bign operator = (const int num) {
char s[numlen];
sprintf(s, "%d", num);
*this = s;
return *this;
}
bign operator = (const char *num) {
len = strlen(num);
while(len > 1 && num[0] == '0') num++, len--;
for(int i = 0;i < len; i++) s[i] = num[len-i-1] - '0';
return *this;
}

void deal() {
while(len > 1 && !s[len-1]) len--;
}

bign operator + (const bign &a) const {
bign ret;
ret.len = 0;
int top = max(len, a.len) , add = 0;
for(int i = 0;add || i < top; i++) {
int now = add;
if(i < len) now += s[i];
if(i < a.len)   now += a.s[i];
ret.s[ret.len++] = now%10;
add = now/10;
}
return ret;
}
bign operator - (const bign &a) const {
bign ret;
ret.len = 0;
int cal = 0;
for(int i = 0;i < len; i++) {
int now = s[i] - cal;
if(i < a.len)   now -= a.s[i];
if(now >= 0)    cal = 0;
else {
cal = 1; now += 10;
}
ret.s[ret.len++] = now;
}
ret.deal();
return ret;
}
bign operator * (const bign &a) const {
bign ret;
ret.len = len + a.len;
for(int i = 0;i < len; i++) {
for(int j = 0;j < a.len; j++)
ret.s[i+j] += s[i]*a.s[j];
}
for(int i = 0;i < ret.len; i++) {
ret.s[i+1] += ret.s[i]/10;
ret.s[i] %= 10;
}
ret.deal();
return ret;
}

//乘以小数，直接乘快点
bign operator * (const int num) {
bign ret;
ret.len = 0;
int bb = 0;
for(int i = 0;i < len; i++) {
int now = bb + s[i]*num;
ret.s[ret.len++] = now%10;
bb = now/10;
}
while(bb) {
ret.s[ret.len++] = bb % 10;
bb /= 10;
}
ret.deal();
return ret;
}

bign operator / (const bign &a) const {
bign ret, cur = 0;
ret.len = len;
for(int i = len-1;i >= 0; i--) {
cur = cur*10;
cur.s[0] = s[i];
while(cur >= a) {
cur -= a;
ret.s[i]++;
}
}
ret.deal();
return ret;
}

bign operator % (const bign &a) const {
bign b = *this / a;
return *this - b*a;
}

bign operator += (const bign &a) { *this = *this + a; return *this; }
bign operator -= (const bign &a) { *this = *this - a; return *this; }
bign operator *= (const bign &a) { *this = *this * a; return *this; }
bign operator /= (const bign &a) { *this = *this / a; return *this; }
bign operator %= (const bign &a) { *this = *this % a; return *this; }

bool operator < (const bign &a) const {
if(len != a.len)    return len < a.len;
for(int i = len-1;i >= 0; i--) if(s[i] != a.s[i])
return s[i] < a.s[i];
return false;
}
bool operator > (const bign &a) const  { return a < *this; }
bool operator <= (const bign &a) const { return !(*this > a); }
bool operator >= (const bign &a) const { return !(*this < a); }
bool operator == (const bign &a) const { return !(*this > a || *this < a); }
bool operator != (const bign &a) const { return *this > a || *this < a; }

string str() const {
string ret = "";
for(int i = 0;i < len; i++) ret = char(s[i] + '0') + ret;
return ret;
}
};
istream& operator >> (istream &in, bign &x) {
string s;
in >> s;
x = s.c_str();
return in;
}
ostream& operator << (ostream &out, const bign &x) {
out << x.str();
return out;
}
// 大数开平方
bign Sqrt(bign x) {
int a[numlen/2];
int top = 0;
for(int i = 0;i < x.len; i += 2) {
if(i == x.len-1) {
a[top++] = x.s[i];
}
else
a[top++] = x.s[i] + x.s[i+1]*10;
}
bign ret = (int)sqrt((double)a[top-1]);
int xx = (int)sqrt((double)a[top-1]);
bign pre = a[top-1] - xx*xx;
bign cc;
for(int i = top-2;i >= 0; i--) {
pre = pre*100 + a[i];
cc = ret*20;
for(int j = 9;j >= 0; j--) {
bign now = (cc + j)*j;
if(now <= pre) {
ret = ret*10 + j;
pre -= now;
break;
}
}
}
return ret;
}
//s[]为倒着收入的