c_cpp 计算两个顶点之间的所有可能路径

Posted 2021-05-14

// https://www.geeksforgeeks.org/count-possible-paths-two-vertices/
#include<iostream>
#include<list>
#include<vector>
using namespace std;

class graph {
    int v;
    list<int> *adj;

public:
    graph(int v) {
        this->v= v;
        adj= new list<int> [v];
    }
    void addEdge (int u, int w) {
        adj[u].push_back(w);
    }
    int CP (int s, int d);
    void CPUtil (int, int, bool [], int&, vector <int> &);
};
int graph::CP (int s, int d) {
    bool visited[v]={0};
    int pc=0;
    vector <int> v;

    CPUtil (s,d,visited, pc,v);
    return pc;
}
void graph::CPUtil(int s, int d, bool visited[], int &pc, vector <int> &v) {
    visited[s]=1;
    v.push_back(s);

    if (s==d) {
        pc++;
        for (auto i=v.begin(); i!= v.end(); ++i)
            cout<< *i << " ";
        cout<< "\n";
    }
    else {
        list<int>::iterator i;
        for (i=adj[s].begin(); i!=adj[s].end();++i)
            if (!visited[*i])
                CPUtil(*i,d,visited, pc, v);
    }

    visited[s]=0;
    v.erase(v.begin()+v.size()-1);
}

int main() {
    graph g(5);
    g.addEdge(0,1);
    g.addEdge(0,2);
    g.addEdge(0,3);
    g.addEdge(1,4);
    g.addEdge(1,3);
    g.addEdge(2,4);
    g.addEdge(3,2);

    cout<< g.CP(0,4);
}

// https://www.geeksforgeeks.org/count-possible-paths-two-vertices/
#include <iostream>
#include <list>
using namespace std;

class graph {
    int v;
    list <int> *adj;
public:
    graph (int v) {
        this->v = v;
        adj= new list<int> [v];
    }
    void addEdge (int u, int w) {
        adj[u].push_back(w);
    }
    int countPaths (int s, int d);
    void countPathUtil (int, int, bool [], int&);
};
int graph::countPaths(int s, int d) {
    bool visited[v]= {0};
    int pc = 0;
    countPathUtil(s,d, visited, pc);
    return pc;
}
void graph::countPathUtil(int s, int d, bool visited[], int &pc){
    visited[s]=1;

    if (s==d)
        pc++;
    else {
        list<int>::iterator j;
        for (j= adj[s].begin(); j!= adj[s].end(); ++j)
            if (!visited[*j])
                countPathUtil(*j,d,visited, pc);
    }
    visited[s]=0;
}

int main()
{
    graph g(4);
    g.addEdge(0, 1);
    g.addEdge(0, 2);
    g.addEdge(0, 3);
    g.addEdge(2, 0);
    g.addEdge(2, 1);
    g.addEdge(1, 3);

    int s = 2, d = 3;
    cout << g.countPaths(s, d);

    return 0;
}