C++ BigInteger 結構體 模板

C++ BigInteger 結構體 模板

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該結構體重載了大部分的運算符,並支持直接在輸入輸出流中進行讀入與輸出

• string str(): 返回字符串類型的BigInteger
• void clean():清除BigInteger前導0

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源代碼

#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;
}