ACM学习历程—SNNUOJ1132 余数之和(数论)

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <set>
#include <map>
#include <queue>
#include <string>
#define LL long long

using namespace std;

const int UNIT = 10;
struct Bignum
{
    int val[30];
    int len;

    Bignum()
    {
        memset(val, 0, sizeof(val));
        len = 1;
    }

    Bignum operator=(const LL &a)
    {
        LL t, p = a;
        len = 0;
        while (p >= UNIT)
        {
            t = p - (p/UNIT)*UNIT;
            p = p / UNIT;
            val[len++] = t;
        }
        val[len++] = p;
        return *this;
    }

    Bignum operator+(const Bignum &a) const
    {
        Bignum x = a;
        int L;
        L = a.len > len ? a.len : len;
        for (int i = 0; i < L; ++i)
        {
            x.val[i] += val[i];
            if (x.val[i] >= UNIT)
            {
                x.val[i+1]++;
                x.val[i] -= UNIT;
            }
        }
        if (x.val[L] != 0)
            x.len = L+1;
        else
            x.len = L;
        return x;
    }

    Bignum operator-(const Bignum &a) const
    {
        bool flag;
        Bignum x1, x2;
        if (*this > a)
        {
            x1 = *this;
            x2 = a;
            flag = 0;
        }
        else
        {
            x1 = a;
            x2 = *this;
            flag = 1;
        }
        int j, L = x1.len;
        for (int i = 0; i < L; ++i)
        {
            if (x1.val[i] < x2.val[i])
            {
                j = i+1;
                while (x1.val[j] == 0)
                    j++;
                x1.val[j--]--;
                while (j > i)
                    x1.val[j--] += UNIT-1;
                x1.val[i] += UNIT-x2.val[i];
            }
            else
                x1.val[i] -= x2.val[i];
        }
        while (x1.val[x1.len-1] == 0 && x1.len > 1)
            x1.len--;
        if (flag)
            x1.val[x1.len-1] = -x1.val[x1.len-1];
        return x1;
    }

    Bignum operator*(const Bignum &a) const
    {
        Bignum x;
        int i, j, up;
        int x1, x2;
        for (i = 0; i < len; i++)
        {
            up = 0;
            for (j = 0; j < a.len; j++)
            {
                x1 = val[i]*a.val[j] + x.val[i+j] + up;
                if (x1 >= UNIT)
                {
                    x2 = x1 - x1/UNIT*UNIT;
                    up = x1 / UNIT;
                    x.val[i+j] = x2;
                }
                else
                {
                    up = 0;
                    x.val[i+j] = x1;
                }
            }
            if (up != 0)
                x.val[i+j] = up;
        }
        x.len = i + j;
        while (x.val[x.len-1] == 0 && x.len > 1)
            x.len--;
        return x;
    }

    Bignum operator/(const int &a) const
    {
        Bignum x;
        int down = 0;
        for (int i = len-1; i >= 0; --i)
        {
            x.val[i] = (val[i]+down*UNIT) / a;
            down = val[i] + down*UNIT - x.val[i]*a;
        }
        x.len = len;
        while (x.val[x.len-1] == 0 && x.len > 1)
            x.len--;
        return x;
    }

    LL operator%(const LL &a) const
    {
        LL x = 0;
        for (int i = len-1; i >= 0; --i)
            x = ((x*UNIT)%a+val[i]) % a;
        return x;
    }

    bool operator>(const Bignum &a) const
    {
        int now;
        if (len > a.len)
            return true;
        else if (len == a.len)
        {
            now = len - 1;
            while (val[now] == a.val[now] && now >= 0)
                now--;
            if(now >= 0 && val[now] > a.val[now])
                return true;
            else
                return false;
        }
        else
            return false;
    }
}ans, tmp, ttmp;

LL n;

void work()
{
    ans = n;
    ans = ans*ans;
    LL j;
    for (LL i = 1; i <= n; i++)
    {
        j = n/(n/i);
        tmp = i+j;
        ttmp = j-i+1;
        tmp = tmp*ttmp;
        tmp = tmp/2;
        ttmp = n/i;
        tmp = tmp*ttmp;
        ans = ans-tmp;
        i = j;
    }
}

void output()
{
    for (int i = ans.len-1; i >= 0; --i)
        printf("%d", ans.val[i]);
    printf("\n");
}

int main()
{
    //freopen("test.in", "r", stdin);
    while (scanf("%lld", &n) != EOF)
    {
        work();
        output();
    }
    return 0;
}