HDU-1297 Children’s Queue

#include <bits/stdc++.h>
#define pb push_back
#define _for(i,a,b) for(int i = (a);i < (b);i ++)
#define INF 0x3f3f3f3f

using namespace std;
const int maxn = 2000;
class HP
{
    public : int len,s[maxn]; HP() {(*this) = 0;};
    HP(int inte) {(*this)=inte;}; HP(const char*str) {(*this)=str;};
    friend ostream& operator << (ostream &cout,const HP &x);
    HP operator = (int inte); HP operator = (const char*str);
    HP operator * (const HP &b);HP operator + (const HP &b);
    HP operator - (const HP &b);HP operator / (const HP &b);
    HP operator % (const HP &b);int Compare(const HP &b);
    bool operator < (const HP &b);
};

ostream& operator << (ostream &cout,const HP &x)
{for(int i = x.len;i >= 1;i --) cout<<x.s[i];return cout;}

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

HP HP::operator = (int inte)
{
    if(inte==0) {len = 1;s[1] = 0;return (*this);};
    for(len = 0;inte > 0;) {s[++len] = inte%10;inte /= 10;};
    return (*this);
}

HP HP::operator * (const HP&b)
{
    int i,j;HP c;c.len = len+b.len;
    for(i = 1;i <= c.len;i ++) c.s[i] = 0;
    for(i = 1;i <=len;i ++) for(j = 1;j <=b.len;j ++) c.s[i+j-1]+=s[i]*b.s[j];
    for(i = 1;i < c.len;i ++) {c.s[i+1]+=c.s[i]/10;c.s[i]%=10;}
    while(c.s[i]) {c.s[i+1]=c.s[i]/10;c.s[i]%=10;i ++;}
    while(i>1&&!c.s[i]) i--;c.len = i;
    return c;
}

HP HP::operator+(const HP &b)
{
    int i;HP c;c.s[1] = 0;
    for(i = 1;i <=len || i<=b.len || c.s[i];i ++)
    {
        if(i<=len) c.s[i]+=s[i];
        if(i<=b.len) c.s[i]+=b.s[i];
        c.s[i+1]=c.s[i]/10;c.s[i]%=10;
    }
    c.len = i-1;if(c.len==0) c.len = 1;
    return c;
}

HP HP::operator-(const HP&b)
{
    int i, j;HP c;
    for(i = 1,j = 0;i <= len;i ++)
    {
        c.s[i] = s[i]-j;if(i<=b.len) c.s[i]-=b.s[i];
        if(c.s[i]<0){j = 1;c.s[i]+=10;}else j = 0;
    }
    c.len = len;while(c.len>1&&!c.s[c.len]) c.len--;
    return c;
}

int HP::Compare(const HP &y)
{
    if(len>y.len) return 1;
    if(len<y.len) return -1;
    int i = len;
    while((i>1)&&(s[i]==y.s[i])) i--;
    return s[i]-y.s[i];
}

bool HP::operator < (const HP &y)
{
    if(this->Compare(y)>=0)    return false;
    return true;
}

HP HP::operator / (const HP&b)
{
    int i,j;HP d(0),c;
    for(i = len;i > 0;i --)
    {
        if(!(d.len==1 && d.s[1]==0))
            {for(j = d.len;j > 0;j --) d.s[j+1]=d.s[j];++d.len;}
        d.s[1] = s[i]; c.s[i] = 0;
        while((j = d.Compare(b))>=0)
            {d=d-b;c.s[i]++;if(j==0) break;}
    }
    c.len = len;while((c.len>1)&&(c.s[c.len]==0)) c.len--;
    return c;
}

HP HP::operator%(const HP&b)
{
    int i,j;HP d(0);
    for(i = len;i > 0;i --)
    {
        if(!(d.len==1 && d.s[1]==0))
        {for(j = d.len;j > 0;j --) d.s[j+1]=d.s[j];++d.len;}
    d.s[1] = s[i];
    while((j = d.Compare(b))>=0) {d = d-b;if(j==0)break;}
    }
    return d;
}

HP d[maxn];
HP solve(int n)
{
    HP a = 0;
    if(a < d[n])
        return d[n];
    
    return d[n] = solve(n-1)+solve(n-2)+solve(n-4);
}

int main()
{
    int N;
    d[1] = 1;
    d[2] = 2;
    d[3] = 4;
    d[4] = 7;
    for(int i = 4;i <= 1000;i ++)
        solve(i);
    while(~scanf("%d",&N))
    {
        cout << solve(N) << endl;
    }
    return 0; 
}