C++ BigInteger 结构体 模板

C++ BigInteger 结构体 模板

该结构体重载了大部分的运算符并支持直接在输入输出流中进行读入与输出

• string str(): 返回字符串类型的BigInteger
• void clean():清除BigInteger前导0

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) {
        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) {
        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) {
        return !(b > *this);
    }

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

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