Question

I am completing a class lab which takes an adjacency matrix, and determines connectivity among vertices. Although my code runs, it does not give the correct results.

I believe there is a problem with the the second if statement in my while loop. any help is greatly appreciated. Code is below:

#include "graph.h"
#include <assert.h>

using namespace std;

bool Graph::connected(int v,int w) {

    int visited[SIZE] ={0};

    if (v == w)         
        return adj_matrix[v][v];

    Queue<int> Q;      
    Q.Enqueue(v);      

    while (!Q.empty()) {
        int curr = Q.Dequeue();

        if (curr == w)
            return true;

        int z=0;         
        for (int i=0; i<SIZE; i++) {      
            if (adj_matrix[curr][z]==1 && visited[i]==false) {
                Q.Enqueue(z);
                visited[i]==true;
            }   
        }
    }
    return false;  
}

This is the output I am receiving:

0 0 1 0 
0 0 0 0 
0 0 0 0 
0 0 0 1 
vertex 0 is connected to vertices: 
vertex 1 is connected to vertices: 
vertex 2 is connected to vertices: 
vertex 3 is connected to vertices: 3 

Which is clearly missing another connection between 0 and 2 correct?

Answer 1

Look closely at your use of the variables i and z. It appears that z is assigned the value 0, and never changed after that. You may want to try using more descriptive variable names to avoid this sort of confusion.