算法-图的路径查询-广度优先遍历

Posted 2020-11-28 erick-l

#include <cassert>
#include <vector>

template<typename Graph>
class ShortestPath
{
private:
    Graph &G;
    int s; //某一个点
    bool* visited;
    int* from;//路径
    int *ord;//最短距离

public:
    ShortestPath(Graph &graph,int s):G(graph){
        //算法初始化
        assert(s>=0 && s < G.V());

        visited = new bool[G.V()];
        from = new int[G.V()];
        ord = new int[G.V()];

        for(int i =0;i<G.V();i++){
            visited[i] = false;
            from[i] = -1;
            ord[i] = -1;
        }
        this->s = s;

        queue<int> q;
        //广度优先无向图最短路径算法
        q.push(s);
        visited[s] = true;
        ord[s]=0;
        while (!q.empty())
        {
            int v = q.front();
            q.pop();
            typename Graph::adjIterator adj(G,v);
            for(int i =adj.begin();!adj.end();i= adj.next()){
                if(!visited[i]){
                    q.push(i);
                    visited[i] =true;
                    from[i]=v;
                    ord[i] = ord[v] +1
                }
            }
        }
        

    };
    ~Path(){
        delete[] visited;
        delete[] from;
        delete[] ord;
    }
    //从s到w是否有路径
    bool hasPath(int w){
        assert(w>=0 && w<G.V());
        return visited[w];
    }

    //从s到w路径是多少
    void path(int w,vector<int> &vec){
        stack<int> s;
        
        int p = w;
        while (p!=-1){
            s.push(p);
            p = from[p];
        }
        vec.clear();
        while (!s.empty()){
            vec.push_back(s.top());
            s.pop();
        }
    }
    //把路径打印出来
    void showPath(int w){
        vector<int> vec;
        path(w,vec);
        for(int i=0;i<vec.size();i++){
            cout<<vec[i];
            if(i==vec.size()-1)
                cout<<endl;
            else
                cout<<" --> ";
        }

    }
    int lenth(int w){
        assert(w>=0 && w<G.V());
        return ord[w];
    }

};