HDU 1250

简单大数

（要压位，不然会超内存）

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;
const int base = 1000000;
struct BigInt
{
    vector<int> Num;
    BigInt() { Num.clear(); }
    void Set(int n) { Num.clear();  Num.push_back(n); }
    BigInt operator + (const BigInt &a) const
    {
        BigInt c;
        int len1 = Num.size(), len2 = a.Num.size();
        int i;
        for(i = 0; i < len1 && i < len2; ++i)
            c.Num.push_back(Num[i] + a.Num[i]);
        for(; i < len1; ++i) c.Num.push_back(Num[i]);
        for(; i < len2; ++i) c.Num.push_back(a.Num[i]);
        for(int i = 0; i < c.Num.size(); ++i)
        {
            if(c.Num[i] >= base)
            {
                if(i == c.Num.size() - 1) c.Num.push_back(c.Num[i] / base);
                else c.Num[i+1] += c.Num[i] / base;
                c.Num[i] %= base;
            }
        }
        return c;
    }

    void Print()
    {
        int len = Num.size();
        printf("%d",Num[len-1]);
        for(int i = len - 2; i >= 0; --i)
        {
            int k = base / 10;
            while(Num[i] < k)
            {
                printf("0");
                k /= 10;
            }
            printf("%d",Num[i]);
        }
        printf("\n");
    }
}N[500000];

void Init()
{
    N[1].Set(1);N[2].Set(1);
    N[3].Set(1);N[4].Set(1);
    for(int i = 5; ; ++i)
    {
        N[i] = N[i-1] + N[i-2] + N[i-3] + N[i-4];
        if(N[i].Num.size() * 5 > 2005) break;
    }
}

int main()
{
    Init();
    int n;
    while(cin >> n)
    {
        N[n].Print();
    }
    return 0;
}