牛客小白月赛11 Rinne Loves Edges

题库链接：https://ac.nowcoder.com/acm/contest/370/F

code:

#include<bits/stdc++.h>
using namespace std;
int n,m,s;
struct edge
{
    int to;int cost;
};
vector<edge> e[110005];
bool vis[100005];
int mem[100005];
long long dp(int i,int pre)
{
    if(e[i].size()==1&&i!=s)
    {
        return e[i][0].cost;
    }
    if(mem[i]!=-1)return mem[i];
    vis[i]=1;
    long long res=0;
    int nxt;int co;
    edge tmp;
    for(int j=0;j<e[i].size();j++)
    {
        tmp=e[i][j];nxt=tmp.to;if(vis[nxt])continue;
        co=tmp.cost;
        res+=dp(nxt,min(co,pre));
    }
    res=min(res,(long long)pre);
    mem[i]=res;
    return res;
}
int main()
{
    //freopen("in.txt","r",stdin);
    memset(mem,-1,sizeof(mem));
    scanf("%d%d%d",&n,&m,&s);
    int u,v,w;
    edge tmp;
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&u,&v,&w);
        tmp.cost=w;tmp.to=v;
        e[u].push_back(tmp);
        tmp.to=u;
        e[v].push_back(tmp);
    }
    long long ans=dp(s,0x3f3f3f3f);
    cout<<ans<<endl;
    return 0;
}