Find next node in normal Inorder traversal . See following post www . geeksforgeeks . org / inorder - tree - traversal - without - recursion / https :
while ( done1 == false ) { if ( curr1 != NULL ) { push ( s1 , curr1 ) ; curr1 = curr1 -> left ; } else { if ( isEmpty ( s1 ) ) done1 = 1 ; else { curr1 = pop ( s1 ) ; val1 = curr1 -> val ; curr1 = curr1 -> right ; done1 = 1 ; } } }