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WAP to find whether given adjacency matrix represents Graph or Tree?

+5 votes
WAP to find whether given adjacency matrix represents Graph or Tree?
posted Nov 11, 2013 by Prakash Singh

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Every graph is a tree so looks that your question is "WAP to know if a given graph is tree from using its adjacency matrix?"
yes sir you are right every tree is a graph.... actually we have to find cycle... if exist we say its a graph otherwise tree...
Yes see the answer by Anderson....

3 Answers

+4 votes

First simple check is to see whether the given adjacency matrix contains more than (n-1) 1's(in the case of undirected graph (2n-2) 1's). If so it is not a tree. Second simple check is to start a traversal(DFS orBFS) from one of the nodes and look for a node which is already visited. if so it involves a cycle and hence not a tree.

answer Nov 12, 2013 by anonymous
what is n here?
+3 votes
#define TREE 1
#define GRAPH 2

int find(int v, int *p)
    while(v != p[v])
        v = p[v];
    return v;
void union(int i, int j, int *p)
    if(i > j)
        p[i] = j;
        p[j] = i;

int Is_TREE_Or_GRAPH(int a[][] , int n)
    int idx, p[n];
    int  u, u1, v, v1;

    for (idx = 0; idx < n; idx++)
        p[idx] = idx;

    for (row = 0; row < n; row++)
        for (col = 0; col < row; col++)
            if(a[row][col] == 1)
                u = row;
                v = col;
                u1 = find(u, p);
                v1 = find(v, p);
                if (u1 == v1)
                    return GRAPH;
                union(u1, v1, p);
    return TREE;
answer Nov 12, 2013 by Vikas Upadhyay
+1 vote

Keep the simple face in mind to solve this -
A tree is a directed graph if and only if it has n vertices (nodes) with n-1 edges. Now it should be simple to solve.

answer Nov 12, 2013 by Anderson
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