POJ 2449 remmarguts ' Date (A * search for K short circuit)

Transmission Door
This is a bare k short-circuit problem, we will use a A * solution.
We can think of it like this when we design the valuation function H. Because H (n) <= h* (n) and as close as possible to h* (n), we think that we can find a shortest path from the target node to the rest of the node, which must be less than or equal to the actual value. Then a A * from the beginning to search, find a node V, so cnt[v] plus 1. When Cnt[v] > K can be pruned, because this must no longer k short circuit on the line. It's good to be proved by the counter-proof method. You can end the search when the target node is searched for the K-th time.
Note that this problem has a very pit, that is, if the beginning = The end point, then 0 is the shortest way (that is, K to + 1)

Code:

#include <cstdio>#include <queue>#include <cstring>using namespace STD;#define MAXM 100006#define MAXN 1006structnode{intV, W; Node *next;} edge[maxm<<1], *ADJ[MAXN], *mcnt = Edge, *RADJ[MAXN];intDIS[MAXN], S, E, K;BOOLINQ[MAXN];structD//data structure used to represent the search node{intG, H, V; D () {} d (intT1,intT2) {v = t1; g = t2; h = dis[v];}BOOL operator< (ConstD RHS)Const{returnG + H > rhs.g + rhs.h; }};voidAddedge (intUintVintW) {node *t = ++mcnt; T->v = v;    T->w = W;    T->next = Adj[u];    Adj[u] = t;    t = ++mcnt; T->v = u;    T->w = W;    T->next = Radj[v]; RADJ[V] = t;}voidSPFA (intU//SPFA used to preprocess the valuation function H{memset(Dis,0x3f,sizeofDIS);memset(INQ,0,sizeofINQ); Queue<int>Q Q.push (U); Dis[u] =0; Inq[u] =1; while(!q.empty ())        {u = Q.front (); Inq[u] =0; Q.pop (); for(Node *p = radj[u]; p; p = p->next)if(P->w + Dis[u] < Dis[p->v]) {Dis[p->v] = Dis[u] + p->w;if(!inq[p->v])                    {Q.push (P-&GT;V); INQ[P-&GT;V] =1; }            }    }}intCNT[MAXN];intAstar (intU//a* Search{priority_queue<d> q; Q.push (D (U,0)); while(!q.empty ())        {D tmp = Q.top ();        CNT[TMP.V] + +; Q.pop ();if(CNT[TMP.V] > K)Continue;//The pruning mentioned above        if(Cnt[e] = = K)returnTMP.G;//Find answers         for(Node *p = adj[tmp.v]; p; p = p->next) Q.push (D (p->v, TMP.G + p->w)); }return-1;}intM, N;intMain () {intT1, T2, T3;scanf("%d%d", &n, &m); for(inti =1; I <= m; i + +) {scanf("%d%d%d", &t1, &t2, &AMP;T3);    Addedge (T1, T2, T3); }scanf("%d%d%d", &s, &e, &k);if(S = = E)    K + +; SPFA (E);printf("%d\n", Astar (S));return 0;}

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POJ 2449 remmarguts ' Date (A * search for K short circuit)