P1073 最优贸易

//Pro:NOIP2009 T3 P1073 最优贸易

//Sol:先用tarjan缩点，得到一个DAG，然后在DAG上拓扑即可。 

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<stack>
#include<queue>
using namespace std;

const int N=1e5+5;
const int M=5e5+5;

inline int read()
{
    char c=getchar();int num=0;
    for(;!isdigit(c);c=getchar());
    for(;isdigit(c);c=getchar())
        num=num*10+c-'0';
    return num;
}

int n,m;
int head[N],num_edge,num_edg; 
struct Edge
{
    int u,v,nxt;
}edge[M<<1],edg[N];
int prize[N];

inline void add_edge(int u,int v)
{
    edge[++num_edge].u=u;
    edge[num_edge].v=v;
    edge[num_edge].nxt=head[u];
    head[u]=num_edge;
}

inline void add(int u,int v)
{
    edg[++num_edg].v=v;
    edg[num_edg].nxt=head[u];
    head[u]=num_edg;
}

int dfn[N],low[N],tim;
bool insta[N];
int belong[N],cnt;
int maxn[N],minn[N];
stack<int> sta;
void tarjan(int now)
{
    dfn[now]=low[now]=++tim;
    sta.push(now),insta[now]=1;
    for(int i=head[now],v;i;i=edge[i].nxt)
    {
        v=edge[i].v;
        if(!dfn[v])
        {
            tarjan(v);
            low[now]=min(low[now],low[v]);
        }
        else if(insta[v])
            low[now]=min(low[now],dfn[v]);
    }
    if(low[now]==dfn[now])
    {
        int tmp;
        ++cnt;
        minn[cnt]=999999999,maxn[cnt]=-1;
        do
        {
            tmp=sta.top(),sta.pop();
            belong[tmp]=cnt;
            insta[tmp]=0;
            maxn[cnt]=max(maxn[cnt],prize[tmp]);
            minn[cnt]=min(minn[cnt],prize[tmp]);
        }while(tmp!=now);
    }
}

int rudu[N];
queue<int> que;
int f[N];
void topsort()
{
    que.push(belong[1]);
    f[belong[1]]=maxn[belong[1]]-minn[belong[1]];
    int now;
    while(!que.empty())
    {
        now=que.front(),que.pop();
        for(int i=head[now],v;i;i=edg[i].nxt)
        {
            v=edg[i].v;
            --rudu[v];
            minn[v]=min(minn[v],minn[now]);
            f[v]=max(f[now],maxn[v]-minn[v]);
            if(!rudu[v])
                que.push(v);
        }
    }
}

int main()
{
//    freopen("233.in","r",stdin);
    n=read(),m=read();
    for(int i=1;i<=n;++i)
        prize[i]=read();
    for(int i=1,u,v,t;i<=m;++i)
    {
        u=read(),v=read(),t=read();
        add_edge(u,v);
        if(t==2)
            add_edge(v,u);
    }
    for(int i=1;i<=n;++i)
        if(!belong[i])
            tarjan(i);
//    cout<<cnt<<endl;
    memset(head,0,sizeof(head));
    for(int i=1;i<=num_edge;++i)
    {
        if(belong[edge[i].u]!=belong[edge[i].v])
        {
            add(belong[edge[i].u],belong[edge[i].v]);
            ++rudu[belong[edge[i].v]];
        }
    }
    topsort(); 
    printf("%d",f[belong[n]]>0?f[belong[n]]:0);
    return 0;
}