K短路 spfa + A*

#include <stdio.h>
#include <string.h>
#include <queue>
#include <algorithm>
using namespace std;
const int L = 100005;
const int inf = 1<<30;
struct node
{
    int now,g,f;
    bool operator <(const node a)const
    {
        if(a.f == f) return a.g < g;
        return a.f < f;
    }
};
struct edges
{
    int x,y,w,next;
} e[L<<2],re[L<<2];//e是输入给出的定向图，re为其逆向图，用于求t到其他所有点的最短路径

int head[1005],dis[1005],vis[1005],n,m,k,s,t,rehead[1005];

void Init()//初始化
{
    memset(e,-1,sizeof(e));
    memset(re,-1,sizeof(re));
    for(int i = 0; i<=n; i++)
    {
        dis[i] = inf;
        vis[i] = 0;
        head[i] = -1;
        rehead[i] = -1;
    }
}

void AddEdges(int x,int y,int w,int k)
{
    e[k].x = x,e[k].y = y,e[k].w = w,e[k].next = head[x],head[x] = k;
    re[k].x = y,re[k].y = x,re[k].w = w,re[k].next = rehead[y],rehead[y] = k;
}

int relax(int u,int v,int c)
{
    if(dis[v]>dis[u]+c)
    {
        dis[v] = dis[u]+c;
        return 1;
    }
    return 0;
}

void SPFA(int src)
{
    int i;
    dis[src] = 0;
    queue<int> Q;
    Q.push(src);
    while(!Q.empty())
    {
        int u,v;
        u = Q.front();
        Q.pop();
        vis[u] = 0;
        for(i = rehead[u]; i!=-1; i = re[i].next)
        {
            v = re[i].y;
            if(relax(u,v,re[i].w) && !vis[v])
            {
                Q.push(v);
                vis[v] = 1;
            }
        }
    }
}

int Astar(int src,int to)
{
    priority_queue<node> Q;
    int i,cnt = 0;
    if(src == to) k++;//在起点与终点是同一点的情况下，k要+1
    if(dis[src] == inf) return -1;
    node a,next;
    a.now = src;
    a.g = 0;
    a.f = dis[src];
    Q.push(a);
    while(!Q.empty())
    {
        a = Q.top();
        Q.pop();
        if(a.now == to)
        {
            cnt++;
            if(cnt == k)
                return a.g;
        }
        for(i = head[a.now]; i!=-1; i = e[i].next)
        {
            next = a;
            next.now = e[i].y;
            next.g = a.g+e[i].w;
            next.f = next.g+dis[next.now];
            Q.push(next);

        }
    }
    return -1;
}

int main()
{
    int i,j,x,y,w;
    while(~scanf("%d%d",&n,&m))
    {
        Init();
        for(i = 0; i<m; i++)
        {
            scanf("%d%d%d",&x,&y,&w);
            AddEdges(x,y,w,i);
        }
        scanf("%d%d%d",&s,&t,&k);
        SPFA(t);
        printf("%d
",Astar(s,t));
    }

    return 0;
}