图论&搜索：K短路-启发式搜索

判断第k短路的权值是否小于T

直接把队友的代码拿过来了，一定很经典

#include <iostream>
#include <queue>
#include <cstring>
#include <vector>

using namespace std;

const int maxn = 3050;
const int INF = 0x7fffffff;
int N, M, S, E, K, T;
int inq[maxn];
int dis[maxn];
int cnt[maxn];

struct Edge
{
    int u, v, w;
    Edge(int a, int b, int c):u(a), v(b), w(c){}
};

struct Node
{
    int d, v;
    Node(int a, int b):d(a), v(b){}
    bool operator < (const Node &x) const {return d+dis[v]>x.d+dis[x.v];}
};

struct Node1
{
    int d, v;
    Node1(int a, int b):d(a), v(b){}
    bool operator < (const Node1 &x) const {return d>x.d;}
};

vector<Edge> edge1;
vector<Edge> edge2;
vector<int> G1[maxn];
vector<int> G2[maxn];

inline void addedge(int a, int b, int c)
{
    edge1.push_back(Edge(a,b,c));
    G1[a].push_back(edge1.size()-1);
    edge2.push_back(Edge(b,a,c));
    G2[b].push_back(edge2.size()-1);
}

void dijkstra_init()
{
    priority_queue<Node1>Q; 
    memset(inq, 0, sizeof(inq));
    std::fill(dis, dis+maxn, INF);
    dis[E] = 0;
    Q.push(Node1(0, E));
    while(!Q.empty())
    {
        auto x = Q.top(); Q.pop();
        if(inq[x.v]) continue;
        inq[x.v] = true;
        for(int i = 0; i < G2[x.v].size(); ++i)
        {
            Edge &m = edge2[G2[x.v][i]];
            if(dis[m.v]>dis[m.u]+m.w)
            {
                dis[m.v] = dis[m.u]+m.w;
                Q.push(Node1(dis[m.v], m.v));
            }
        }
    }
}

int k_th()
{
    memset(cnt, 0, sizeof(cnt)); 
    priority_queue<Node>Q;  
    if(dis[S]>=INF)  return -1;  
    Node e(0, S);
    Q.push(e);  

    while(!Q.empty())  
    {  
        Node x = Q.top();Q.pop();  
        
        cnt[x.v]++;
        
        if(x.v == E)
        {
            if(x.d>T) return -1;
            if(cnt[x.v] == K) return x.d;  
        }
        
        if (cnt[x.v] > K)    continue;

        for(unsigned int i = 0; i < G1[x.v].size(); i++)  
        {  
            Node n(x.d+edge1[G1[x.v][i]].w, edge1[G1[x.v][i]].v);
            if(cnt[n.v] != K)
            Q.push(n);  
        }  
    }  
    return -1;
}

int main()
{
    while(scanf("%d%d", &N, &M) != EOF)
    {
        edge1.clear();
        edge2.clear();

        for(int i = 0; i < maxn; ++i)
        {
            G1[i].clear();
            G2[i].clear();
        }

        
        scanf("%d%d%d%d", &S, &E, &K, &T);
        
        for(int i = 1; i <= M; ++i)
        {
            int a, b, c;
            scanf("%d%d%d", &a, &b, &c);
            addedge(a, b, c);
        }

        dijkstra_init();
        
        int ans = k_th();

        if(ans <= T && ans != -1) printf("yareyaredawa
");
        else printf("Whitesnake!
");
    }
    return 0;
}