Edges of the tree
graph [ 1 ] . append ( 2 ) NEW_LINE graph [ 1 ] . append ( 3 ) NEW_LINE graph [ 2 ] . append ( 4 ) NEW_LINE graph [ 2 ] . append ( 5 ) NEW_LINE dfs ( 1 , 1 , 0 ) NEW_LINE primeHeightNode ( N ) NEW_LINE