uva 10198

backtrak失敗 TLE

發現有DP性質，就直接DP下去AC

//====================================================================||
// Name        : Counting.cpp                                              ||
// Date : 2013/7/20 下午1:51:45                                               ||
// Author : GCA                                                       ||
//                  6AE7EE02212D47DAD26C32C0FE829006                  ||
//====================================================================||
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
using namespace std;
#ifdef ONLINE_JUDGE
#define ll "%lld"
#else
#define ll "%I64d"
#endif
typedef unsigned int uint;
typedef long long int Int;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\n")
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()
#define De(x)printf(#x"%d\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\
    printf("%d ",dp[htx][hty]);}Pln();}
#define M 10011
#define PII pair<int,int>
#define PB push_back
#define oo INT_MAX
#define Set_oo 0x3f
#define Is_debug true
#define debug(...) if(Is_debug)printf("DEBUG: "),printf(__VA_ARGS__)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define eps 1e-6
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
    int tmp=min(x,y);
    return min(tmp,z);
}
int max3(int x,int y,int z){
    int tmp=max(x,y);
    return max(tmp,z);
}
class bignum{
public:
    Int n[150];
    const static int maxn=150;
    const static int base=10000;
    bignum(){
        Set(n,0);
    }
    void clear(){
        Set(n,0);
    }
    bignum add(Int x){
        bignum ans;
        Int c=0;
        for(int i=0;i<maxn;i++){
            Int tmp=n[i]+x+c;
            x=0;
            ans.n[i]=tmp%base;
            c=tmp/base;
        }
        return ans;
    }
    bignum mul(int a){
        bignum ans;
        Int c=0;
        for(int i=0;i<maxn;i++){
            Int tmp=n[i]*a+c;
            ans.n[i]+=tmp%base;
            c=tmp/base;
            for(int j=i+1;j<maxn;j++){
                Int tmp2=ans.n[j]+c;
                ans.n[j]=tmp2%base;
                c=tmp2/base;
                if(!c)break;
            }
        }
        return ans;
    }
    bignum operator+(bignum &d)const{
        bignum ans;
        Int c=0;
        for(int i=0;i<maxn;i++){
            Int tmp=n[i]+d.n[i]+c;
            ans.n[i]=tmp%base;
            c=tmp/base;
        }
        return ans;
    }
    bool operator!=(bignum &d)const{
        for(int i=0;i<maxn;i++){
            if(d.n[i]==n[i])return false;
        }
        return true;
    }
    void print(){
        int i=maxn-1;
        for(;i>0;i--)if(n[i]!=0)break;
        printf("%lld",n[i--]);
        for(;i>=0;i--){
            printf("%04lld",n[i]);
        }Pln();
    }
};
int n;
bignum cnt;
bignum dp[1005];
bignum minu;
void pre(){
    dp[1]=dp[1].add(2);
    dp[2]=dp[2].add(5);
    dp[3]=dp[3].add(13);
    for(int i=4;i<1001;i++){
        dp[i]=dp[i-1].mul(2)+dp[i-2]+dp[i-3];
    }
}

int main() {
    ios_base::sync_with_stdio(0);
    pre();
    while(~scanf("%d",&n)){
        dp[n].print();
    }

















}