E. Coin Troubles

http://codeforces.com/contest/284/problem/E

思维很重要呀 原来是一个背包呀

代码：

#include<iostream>

#include<cmath>

#include<cstdio>

#include<string>

#include<cstring>

#include<vector>

#include<stack>

#include<queue>

#include<map>

#include<set>

#include<algorithm>



#define LL long long



using namespace std;



const int INF=0x3f3f3f3f;

const int MOD=1000000007;

const int N=305;

const int M=100005;

int a[N],next[N];

bool head[N];

int dp[M];

vector< vector<int> >h;

void packComplete(int cost,int V)

{

    for(int v=cost;v<=V;++v)

    dp[v]=(dp[v]+dp[v-cost])%MOD;

}

int main()

{

    //freopen("data.in","r",stdin);

    int n,q,t;

    while(cin>>n>>q>>t)

    {

        h.clear();

        memset(next,0,sizeof(next));

        for(int i=1;i<=n;++i)

        cin>>a[i];

        memset(head,true,sizeof(head));

        while(q--)

        {

            int l,r;

            cin>>l>>r;

            head[r]=false;

            next[l]=r;

        }

        int line[N],m;

        for(int i=1;i<=n;++i)

        if(head[i]==true)

        {

            int l=i;

            m=0;

            line[m++]=l;

            while(next[l]!=0)

            {

                l=next[l];

                line[m++]=l;

            }

            h.push_back(vector<int>(line,line+m));

        }

        int num=0;

        for(int unsigned i=0;i<h.size();++i)

        num+=h[i].size();

        if(num<n)

        {cout<<"0"<<endl;continue;}

        memset(dp,0,sizeof(dp));

        int V=t;

        int k=0;

        dp[0]=1;

        for(unsigned int i=0;i<h.size();++i)

        {

            int tmp=0;

            for(unsigned int j=0;j<h[i].size();++j)

            {

                int l=h[i][j];

                if(k<=V)

                k=k+(h[i].size()-1-j)*a[l];

                if(tmp>V) continue;

                tmp+=a[l];

                if(tmp<=V)

                packComplete(tmp,V);

            }

        }

        if(k>V)

        {cout<<"0"<<endl;continue;}

        cout<<dp[V-k]<<endl;

    }

    return 0;

}