K短路 spfa + A*

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  1 #include <stdio.h>  2 #include <string.h>  3 #include <queue>  4 #include <algorithm>  5 using namespace std;  6 const int L = 100005;  7 const int inf = 1<<30;  8 struct node  9 { 10     int now,g,f; 11     bool operator <(const node a)const 12     { 13         if(a.f == f) return a.g < g; 14         return a.f < f; 15     } 16 }; 17 struct edges 18 { 19     int x,y,w,next; 20 } 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 21  22 int head[1005],dis[1005],vis[1005],n,m,k,s,t,rehead[1005]; 23  24 void Init()//初始化 25 { 26     memset(e,-1,sizeof(e)); 27     memset(re,-1,sizeof(re)); 28     for(int i = 0; i<=n; i++) 29     { 30         dis[i] = inf; 31         vis[i] = 0; 32         head[i] = -1; 33         rehead[i] = -1; 34     } 35 } 36  37 void AddEdges(int x,int y,int w,int k) 38 { 39     e[k].x = x,e[k].y = y,e[k].w = w,e[k].next = head[x],head[x] = k; 40     re[k].x = y,re[k].y = x,re[k].w = w,re[k].next = rehead[y],rehead[y] = k; 41 } 42  43 int relax(int u,int v,int c) 44 { 45     if(dis[v]>dis[u]+c) 46     { 47         dis[v] = dis[u]+c; 48         return 1; 49     } 50     return 0; 51 } 52  53 void SPFA(int src) 54 { 55     int i; 56     dis[src] = 0; 57     queue<int> Q; 58     Q.push(src); 59     while(!Q.empty()) 60     { 61         int u,v; 62         u = Q.front(); 63         Q.pop(); 64         vis[u] = 0; 65         for(i = rehead[u]; i!=-1; i = re[i].next) 66         { 67             v = re[i].y; 68             if(relax(u,v,re[i].w) && !vis[v]) 69             { 70                 Q.push(v); 71                 vis[v] = 1; 72             } 73         } 74     } 75 } 76  77 int Astar(int src,int to) 78 { 79     priority_queue<node> Q; 80     int i,cnt = 0; 81     if(src == to) k++;//在起点与终点是同一点的情况下，k要+1 82     if(dis[src] == inf) return -1; 83     node a,next; 84     a.now = src; 85     a.g = 0; 86     a.f = dis[src]; 87     Q.push(a); 88     while(!Q.empty()) 89     { 90         a = Q.top(); 91         Q.pop(); 92         if(a.now == to) 93         { 94             cnt++; 95             if(cnt == k) 96                 return a.g; 97         } 98         for(i = head[a.now]; i!=-1; i = e[i].next) 99         {100             next = a;101             next.now = e[i].y;102             next.g = a.g+e[i].w;103             next.f = next.g+dis[next.now];104             Q.push(next);105 106         }107     }108     return -1;109 }110 111 int main()112 {113     int i,j,x,y,w;114     while(~scanf("%d%d",&n,&m))115     {116         Init();117         for(i = 0; i<m; i++)118         {119             scanf("%d%d%d",&x,&y,&w);120             AddEdges(x,y,w,i);121         }122         scanf("%d%d%d",&s,&t,&k);123         SPFA(t);124         printf("%d\n",Astar(s,t));125     }126 127     return 0;128 }
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