c – 使用A *算法进行图遍历

嘿,我是AI学生,我会尝试我的作业,即实现A *算法,以便遍历图表.我使用c代码,我现在所做的是代码,它只是一个Graph类插入和顶点函数.
但现在我对如何定义成本函数感到困惑(f = h(n)g(n))…

任何代码参考或解释A *如何适用于图表将有助于我.我在google中发现的是关于通过*进行寻路,它与遍历图没有任何关系.

#include <iostream>
using namespace std;

class Graph;
class node {
    friend class Graph;
private:
    char data;
    int cost;
    node *next;
    node *vlist;
    bool goal;
    bool visited;
public:
    node(char d,int c, bool g){
        cost = c;
        goal = g;
        next = NULL;
        data = d;
        vlist = NULL;
        visited = false;
    }
};

class Graph {
private:
    node *Headnodes;
    char n;
public:
    Graph ()
    {
        Headnodes = NULL;
    }
    void InsertVertex(char n, int c, bool g);
    void InsertEdge(char n, char m, int c);
    void PrintVertices();
    void Expand(char n);
};

/////////////////
//  INSERTION  //
/////////////////
void Graph::InsertVertex(char n, int c, bool g){
    node *temp = new node(n,c,g);
    if(Headnodes==NULL)
    {
        Headnodes=temp;
        return;
    }

    node *t=Headnodes;
    while(t->vlist!=NULL)
        t=t->vlist;
    t->vlist=temp;
}

void Graph::InsertEdge(char n, char m, int c){
    int temp_cost = 0;
    if(Headnodes==NULL)
        return;

    node *x=Headnodes;
    while(x!=NULL){
        if(x->data==m)
            temp_cost = (x->cost+c);
        x = x->vlist;
    }
    node *t=Headnodes;
    node *temp=new node(m,temp_cost,false);

    while(t!=NULL){
        if(t->data==n){
            node *s=t;
            while(s->next!=NULL)
                s=s->next;
            s->next=temp;
        }
        t=t->vlist;
    }
}

int min_cost = 1000;
bool enough = false;
void Graph::PrintVertices(){
    node *t=Headnodes;
    while(t!=NULL){
        cout<<t->data<<"\t";
        t=t->vlist;
    }
}

void Graph::Expand(char n){
    cout << n << "\t";
    char temp_min;
    node *t=Headnodes;
    while(t!=NULL){
        if(t->data==n && t->visited == false){
            t->visited = true;
            if (t->goal)
                return;
            while(t->next!=NULL){
                if (t->next->cost <= min_cost){
                    min_cost=t->next->cost;
                    temp_min = t->next->data;
                }
                t = t->next;
            }
        }
        t=t->vlist;
    }
    Expand(temp_min);
}

int main(){
    Graph g;
    g.InsertVertex('A',5,false);
    g.InsertVertex('B',1,false);
    g.InsertVertex('C',9,false);
    g.InsertVertex('D',5,false);
    g.InsertVertex('E',1,false);
    g.InsertVertex('F',3,false);
    g.InsertVertex('G',2,false);
    g.InsertVertex('J',1,false);
    g.InsertVertex('K',0,true);

    g.InsertEdge('A','B',2);
    g.InsertEdge('A','C',1);
    g.InsertEdge('B','A',2);
    g.InsertEdge('B','D',1);
    g.InsertEdge('B','E',1);
    g.InsertEdge('C','A',1);
    g.InsertEdge('C','F',1);
    g.InsertEdge('C','G',1);
    g.InsertEdge('E','J',3);
    g.InsertEdge('E','K',3);

    g.PrintVertices();

    cout<<"\n\n";
    g.Expand('A');

    return 0;
}

解决方法:

你所拥有的只是一个图搜索算法.

你忘记了A *算法的本质,即来自启发式计算的h(n)成本.

你必须实现一个方法,h(n)将根据你的heuritics计算从实际路径到最终路径的可能成本,这个值将用于计算行走成本：

f'(n)= g(n)h'(n),是g(n)已知的成本,在您的情况下,x->成本.

g(n) is the total distance cost it has
taken to get from the starting
position to the current location.

h'(n) is the estimated distance cost from
the current position to the goal
destination/state. A heuristic
function is used to create this
estimate on how far away it will take
to reach the goal state.

f'(n) is the sum of g(n) and h'(n).
This is the current estimated shortest
path. f(n) is the true shortest path
which is not discovered until the A*
algorithm is finished.

所以,你要做的是：

>实现方法heuristic_cost(actual_node,final_node);
>将此值与实际成本一起使用,例如之前的等式,例如：min_cost = t-> next-> cost heuristic_cost(t-> next,final_node);

我真的很喜欢这里的解释：http://www.policyalmanac.org/games/aStarTutorial.htm,比维基百科的解释清晰.

标签：a-star,c,algorithm,graph,traversal
来源： https://codeday.me/bug/20190903/1797559.html