POj 2449 Remmarguts' Date K短路 A*+SPFA

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第一道A*，网上教程一大把就不说了。
#include <cstdio>#include <algorithm>#include <cstring>#include <queue>#include <vector>using namespace std;const int INF = 999999999;const int maxn = 1010;struct edge{    int u, v, w;    int next;    edge(){}}G1[100010], G2[100010];struct A{    int f, g, v;    A() {}    A(int f, int g, int v) : f(f), g(g), v(v) {}    bool operator <(const A a) const    {        if(a.f == f)            return a.g < g;        return a.f < f;    }};int d[maxn], first[maxn], head[maxn];bool inq[maxn];int n, m, cnt1, cnt2;void AddEdge(int u, int v, int w){    G1[cnt1].v = v;    G1[cnt1].w = w;    G1[cnt1].next = first[u];    first[u] = cnt1++;    G2[cnt2].v = u;    G2[cnt2].w = w;    G2[cnt2].next = head[v];    head[v] = cnt2++;}bool SPFA(int s){    memset(inq, false, sizeof(inq));    for(int i = 0; i <= n; i++)        d[i] = INF;    d[s] = 0;    queue <int> Q;    Q.push(s);    inq[s] = true;    while(!Q.empty())    {        int u = Q.front(); Q.pop();        inq[u] = false;        for(int i = head[u]; i != -1; i = G2[i].next)        {            edge e = G2[i];            int v = e.v;            int w = e.w;            if(d[v] > d[u] + w)            {                d[v] = d[u] + w;                if(!inq[v])                {                    inq[v] = true;                    Q.push(v);                }            }        }    }}int AStar(int s, int t, int K){    if(d[s] == INF)        return -1;    int cnt = 0;    priority_queue<A> Q;    if(s == t)        K++;    Q.push(A(d[s], 0, s));    while(!Q.empty())    {        A a = Q.top();        Q.pop();        if(a.v == t)        {            cnt++;            //printf("%d\n", a.g);            if(cnt == K)                return a.g;        }        int u = a.v;        for(int i = first[u]; i != -1; i = G1[i].next)        {            edge e = G1[i];            A b;            b.v = e.v;            b.g = a.g + e.w;            b.f = b.g + d[b.v];            Q.push(b);        }    }    return -1;}int main(){    memset(first, -1, sizeof(first));    memset(head, -1, sizeof(head));    scanf("%d %d", &n, &m);    for(int i = 0; i < m; i++)    {        int u, v, w;        scanf("%d %d %d", &u, &v, &w);        AddEdge(u, v, w);    }    int s, t, k;    scanf("%d %d %d", &s, &t, &k);    SPFA(t);    printf("%d\n", AStar(s, t, k));    return 0;}
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