UVa 10917 Walk Through the Forest（最短路＋DP）

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <vector>
#define INF 10000000
using namespace std;
int N,M;
struct edge{
    int s,t,c;
};

vector <edge> E;
vector <int> G[1005];
int d[1005];
bool vis[1005];
int p[1005];

int dp[1005];

int solve(int n){
    if(dp
) return dp
;
    for(int i=0;i<G
.size();i++){
        edge &tmp=E[G
[i]];
        if(d[tmp.t]<d
){
           dp
+=solve(tmp.t);
        }
    }
    return dp
;
}

void addedge(int s,int t,int cost){
    E.push_back(edge{s,t,cost});
    G[s].push_back(E.size()-1);
}

struct HNode{
    int d,u;
    bool operator <(const HNode &obj)const{
        return d>obj.d;
    }
};

void Dij(int s){
    for(int i=1;i<=N;i++){
        d[i]=INF;
    }

    d[s]=0;
    memset(vis,0,sizeof(vis));
    priority_queue<HNode> Q;
    Q.push(HNode{0,s});
    while(!Q.empty()){
        int u=Q.top().u;
        Q.pop();
        if(vis[u]) continue;
        vis[u]=1;
        for(int i=0;i<G[u].size();i++){
            edge &tmp=E[G[u][i]];
            if(d[tmp.t]>d[u]+tmp.c){
                d[tmp.t]=d[u]+tmp.c;
                p[tmp.t]=u;
                Q.push(HNode{d[tmp.t],tmp.t});
            }
        }
    }
}

int main(){
    while(~scanf("%d",&N)){
        for(int i=1;i<=N;i++){
            G[i].clear();
        }
        E.clear();
        if(!N) break;
        scanf("%d",&M);
        for(int i=0;i<M;i++){
            int s,t,c;
            scanf("%d%d%d",&s,&t,&c);
            addedge(s,t,c);
            addedge(t,s,c);
        }
        Dij(2);
        memset(dp,0,sizeof(dp));
        dp[2]=1;
        solve(1);
        for(int i=1;i<=N;i++){
            //cout<<i<<' '<<dp[i]<<endl;
        }
        printf("%d\n",solve(1));
    }
    return 0;
}