C++ BigInteger 结构体 模板

C++ BigInteger 结构体 模板

源代码

#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>
const int maxn = 500;
using namespace std;
struct BigInteger{
int len, s[maxn];

BigInteger() {
memset(s, 0, sizeof(s));
len = 1;
}

BigInteger(int num) {
*this = num;
}

BigInteger(const char* num) {
*this = num;
}

BigInteger operator = (int num) {
char s[maxn];
sprintf(s, "%d", num);
*this = s;
return *this;
}

BigInteger operator = (const char* num) {
len = strlen(num);
for(int i = 0; i < len; i++)
s[i] = num[len - i - 1] - '0';
return *this;
}

string str() const {
string res = "";
for(int i = 0; i < len; i++)
res = (char)(s[i] + '0') + res;
if(res == "")
res = "0";
return res;
}

BigInteger operator + (const BigInteger& b) const{
BigInteger c;
c.len = 0;
for(int i = 0, g = 0; g || i < max(len, b.len); i++) {
int x = g;
if(i < len)
x += s[i];
if(i < b.len) x += b.s[i];
c.s[c.len++] = x % 10;
g = x / 10;
}
return c;
}

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

BigInteger operator * (const BigInteger& b) const{
BigInteger c; c.len = len + b.len;
for(int i = 0; i < len; i++)
for(int j = 0; j < b.len; j++)
c.s[i+j] += s[i] * b.s[j];
for(int i = 0; i < c.len-1; i++){
c.s[i+1] += c.s[i] / 10;
c.s[i] %= 10;
}
c.clean();
return c;
}

BigInteger operator - (const BigInteger& b) const{
BigInteger c; c.len = 0;
for(int i = 0, g = 0; i < len; i++) {
int x = s[i] - g;
if(i < b.len)
x -= b.s[i];
if(x >= 0)
g = 0;
else {
g = 1;
x += 10;
}
c.s[c.len++] = x;
}
c.clean();
return c;
}

bool operator < (const BigInteger& b) const{
if(len != b.len) return len < b.len;
for(int i = len-1; i >= 0; i--)
if(s[i] != b.s[i])
return s[i] < b.s[i];
return false;
}

bool operator > (const BigInteger& b) const{
return b < *this;
}

bool operator <= (const BigInteger& b) const{
return (b > *this);
}

bool operator >= (const BigInteger& b) const{
return (b < *this);
}

bool operator == (const BigInteger& b) const{
return !(b < *this) && !(*this < b);
}

bool operator != (const BigInteger& b) const{
return !(*this == b);
}

BigInteger operator += (const BigInteger& b) {
*this = *this + b;
return *this;
}

BigInteger operator -= (const BigInteger& b) {
*this = *this - b;
return *this;
}

BigInteger operator ++ (int) {
*this = *this + 1;
return *this;
}

BigInteger operator -- (int) {
*this = *this - 1;
return *this;
}

BigInteger operator ++ () {
*this = *this + 1;
return *this;
}

BigInteger operator -- () {
*this = *this - 1;
return *this;
}
};

istream& operator >> (istream &in, BigInteger& x) {
string s;
in >> s;
x = s.c_str();
return in;
}

ostream& operator << (ostream &out, const BigInteger& x) {
out << x.str();
return out;
}