最短路和次短路

include

#include<cstring>
#include<algorithm>
#include<cstring>
#include<queue>
#include<cstdio>
#define CLR(a,b) memset(a,b,sizeof(a))
using namespace std;
typedef long long ll;
const int maxn = 1e3 + 10;
const int INF = 0x3f3f3f3f;
struct node
{
    int type;
    int x;
    int d;
    node();
    node(int a,int b,int c){
        type = a;
        x = b;
        d = c;
    }
    bool operator < (const node &a) const{
        return d > a.d;
    }
};

struct edge
{
    int from,to,next,w;
}edge[maxn*10];

int head[maxn],dis[maxn][2],cnt[maxn][2],vis[maxn][2];
int tol;

void init()
{
    tol = 0;
    CLR(head,-1);
    CLR(dis,0x3f);
    CLR(cnt,0);
    CLR(vis,0);
}

void addedge(int u,int v,int w)
{
    edge[tol].from=u;
    edge[tol].to=v;
    edge[tol].w=w;
    edge[tol].next=head[u];
    head[u]=tol++;
}

void dijkstra(int s)
{
    priority_queue<node> q;
    q.push(node(0,s,0));
    dis[s][0] = 0;
    cnt[s][0] = 1;

    while(!q.empty()){
        node now=q.top();
        q.pop();
        int u=now.x;
        if(vis[u][now.type]==1)continue;
        vis[u][now.type]=1;

        for(int i=head[u];~i;i=edge[i].next){
            int d=edge[i].w;
            int v=edge[i].to;
            if(d+now.d<dis[v][0]){
                dis[v][1]=dis[v][0];
                dis[v][0]=d+now.d;
                cnt[v][1]=cnt[v][0];
                cnt[v][0]=cnt[u][now.type];
                q.push(node(0,v,dis[v][0]));
                q.push(node(1,v,dis[v][1]));
            }
            else if(d+now.d==dis[v][0]){
                cnt[v][0]+=cnt[u][now.type];
            }
            else if(d+now.d<dis[v][1]){
                dis[v][1]=d+now.d;
                cnt[v][1]=cnt[u][now.type];
                q.push(node(1,v,dis[v][1]));
            }
            else if(d+now.d==dis[v][1]){
                cnt[v][1]+=cnt[u][now.type];
            }
        }
    }
}

int main()
{
    int t,u,v,w,n,m,s,e;
    scanf("%d",&t);
    while(t--){
        init();
        scanf("%d%d",&n,&m);
        for(int i = 1; i <= m; i++){
            scanf("%d%d%d",&u,&v,&w);
            addedge(u,v,w);
        }
        scanf("%d%d",&s,&e);
        dijkstra(s);
//        cout<<dis[e][0]<<" "<<dis[e][1]<<endl;
//        cout<<cnt[e][0]<<" "<<cnt[e][1]<<endl;
        if(dis[e][1]-dis[e][0]==1) printf("%d\n",cnt[e][0]+cnt[e][1]);
        else printf("%d\n",cnt[e][0]);
    }
    return 0;
}