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  • 初涉A*剪枝

    挖坑防忘,天亮补题解。

    #include <algorithm>
    #include <iostream>
    #include <cstring>
    #include <cstdlib>
    #include <cstdio>
    #include <queue>
    #include <cmath>
    #include <stack>
    #include <map>
    
    #pragma comment(linker, "/STACK:1024000000");
    #define EPS (1e-8)
    #define LL long long
    #define ULL unsigned long long LL
    #define _LL __int64
    #define _INF 0x3f3f3f3f
    #define Mod 1000000007
    
    using namespace std;
    
    const int MAXN = 100100;
    
    struct N
    {
        int u,v,w,next,ty;
    }edge[2*MAXN];
    
    int head[MAXN];
    
    int Top;
    
    void Link(int u,int v,int w,int ty)
    {
        edge[Top].ty = ty;
        edge[Top].v = v;
        edge[Top].w = w;
        edge[Top].next = head[u];
        head[u] = Top++;
    }
    
    int ans[1010];
    
    int w[1010][1010];
    
    int H[1010];
    
    struct Q
    {
        int v,g,h,f;
        bool operator < (const Q &a) const
        {
            return a.f < f;
        }
    };
    
    void Init_H(int t)
    {
        Q s,f;
        s.f = 0;
        s.v = t;
    
        memset(H,-1,sizeof(H));
        H[t] = 0;
    
        priority_queue<Q> q;
        q.push(s);
    
        while(q.empty() == false)
        {
            f = q.top();
            q.pop();
    
            H[f.v] = (H[f.v] == -1 ? f.f : H[f.v]);
    
            for(int p = head[f.v]; p != -1; p = edge[p].next)
            {
                if(edge[p].ty == 2)
                {
                    if(H[edge[p].v] == -1)
                    {
                        s.v = edge[p].v;
                        s.f = f.f + edge[p].w;
                        q.push(s);
                    }
                }
            }
        }
    }
    
    void bfs(int h,int e,int k)
    {
        Q f,s;
        priority_queue<Q> q;
        f.g = 0;
        f.h = H[h];
        f.f = f.h + f.g;
        f.v = h;
    
        q.push(f);
    
        while(q.empty() == false)
        {
            f = q.top();
            q.pop();
    
            if(f.g != 0)
            {
                w[f.v][++ans[f.v]] = f.g;
    
                if(f.v == e && ans[f.v] == k)
                    return ;
            }
    
    
            for(int p = head[f.v]; p != -1; p = edge[p].next)
            {
                if(edge[p].ty == 1)
                {
                    s.v = edge[p].v;
                    s.h = H[edge[p].v];
                    s.g = f.g + edge[p].w;
                    s.f = s.h + s.g;
                    q.push(s);
                }
            }
    
        }
    
    }
    
    int main()
    {
    
        int n,m;
    
        int u,v,ww,i;
    
        while(scanf("%d %d",&n,&m) != EOF)
        {
            memset(head,-1,sizeof(head));
    
            Top = 0;
    
            for(i = 0;i < m; ++i)
            {
                scanf("%d %d %d",&u,&v,&ww);
                Link(u,v,ww,1);
                Link(v,u,ww,2);
            }
    
            int s,t,k;
    
            scanf("%d %d %d",&s,&t,&k);
    
            Init_H(t);
    
            memset(ans,0,sizeof(ans));
    
            bfs(s,t,k);
    
            if(ans[t] < k)
            {
                printf("-1
    ");
            }
            else
            {
                printf("%d
    ",w[t][k]);
            }
    
        }
        return 0;
    }
    

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  • 原文地址:https://www.cnblogs.com/zfyouxi/p/3867923.html
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