使用深度優先遍歷即可獲得兩點間的一條路徑

定義 Path.h 實現獲取路徑

 #include <stack>
 #include <iostream>
 #include <cassert>

 using namespace std;

template <typename Graph>
class Path{

private:
    Graph &G;
    int s;
    bool *visited;
    int *from;

    void dfs(int v){
        visited[v] = true;
 


        typename Graph::adjIterator adj(G, v);
        for ( int i = adj.begin(); !adj.end(); i = adj.next() ){
            if ( !visited[i] ){
                from[i] = v;
                dfs(i);
            }
        }
    }

public:
    Path(Graph &graph, int s):G(graph){

        //演算法初始化
        assert
 
( s >= 0 && s < G.V() );

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

        //尋路演算法
        dfs(s);

    }

    ~Path() {
        delete[
 
] visited;
        delete[] from;
    }

    bool hasPath(int w){
        assert( w >= 0 && w < G.V() );
        return visited[w];
    }

    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();
        }
    }

    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<<" -> ";
        }
    }
};

測試程式如下

#include <ctime>
#include <cstdlib>
#include "SparseGraph.h"
#include "DenseGraph.h"
#include "ReadGraph.h"
#include "Path.h"

using namespace std;

int main()
{
    string filename = "testG2.txt";
    SparseGraph g = SparseGraph( 7, false );
    ReadGraph<SparseGraph> readGraph( g, filename );
    g.show();
    cout<<endl;

    Path<SparseGraph> dfs( g, 0 );
    cout<<"DFS : ";
    dfs.showPath(6);

    return 0;
}

上面呼叫的其他標頭檔案見上篇部落格

輸出為


獲取兩點之間的路徑可以用來檢視圖中的環