题解

#include <bits/stdc++.h>


using namespace std;


const int maxn = 1e3;


struct Edge
{
    int to,w,next;
}edge[maxn];
int head[maxn], cnt = 0;
void add_edge(int u, int to, int w)
{
    edge[cnt].to = to;
    edge[cnt].w = w;
    edge[cnt].next = head[u];
    head[u] = cnt++;
}
int card[maxn]={},dis[maxn],visNode[maxn],visCard[maxn];
int n,m,k,c;


int ans = 0x3f3f3f3f;
void dfs(int u, int pp)
{
    if(u == c)
    {
        ans = min(ans, pp);
        return;
    }
    for(int i = head[u];i!=-1;i=edge[i].next)
    {
        int to = edge[i].to;
        int w = edge[i].w;
        int cardValue = card[w];


        if(visNode[to] == 0)
        {
            visCard[w] = 1;
            visNode[to] = 1;
            card[w] = 0;
            dfs(to,pp + cardValue);
            card[w] = cardValue;
            visNode[to] = 0;
        }
    }
}

int main()
{
    while(cin>>n>>m>>k>>c)
    {
        for(int i = 0;i<maxn;i++)
        {
            ans = 0x3f3f3f3f;
            dis[i] = 0x3f3f3f3f;
            card[i] = 0;
            head[i] = -1;
            visNode[i] = 0;
            visCard[i] = 0;
            memset(edge,0,sizeof(edge));
        }


        for(int i = 0;i<m;i++)
        {
            int u,v,w;
            cin>>u>>v>>w;
            add_edge(u,v,w);
        }
        for(int i = 0;i<k;i++)
        {
            int o ,p;
            cin>>o>>p;
            card[o] = p;
        }
        dfs(1,0);
        cout<<ans<<endl;


    }
    return 0;
}