Problem # 16 : A tree or not a tree

Write a function TREE(M N A()) to find out whether a given graph is a tree or not.

M stands for the number of nodes (points) and N stands for the number of connections in the graph. If there is a connection between node P & Q then cells A(<connection> 1) and A(<connection> 2) are set to P & Q.

Sample Output
M=5 N=5 (5 stations and 5 connections)

and array A() contains.

1	2
1	3
5	2
3	4
3	5

TREE(5 5 A()) should return 0 as it is not a tree.

If M=7 N=6 and array A() has values

1	2
1	3
3	5
3	4
6	2
7	2

TREE(M N A()) should return -1 since the graph is a tree.

if M=8 N=5 and A() contains

1	2
1	3
5	2
3	4
6	7

TREE(8 5 A()) should return 0 since it is not a single tree.

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