Check if each internal node of BST has only one child
class BinaryTree { boolean hasOnlyOneChild ( int pre [ ] , int size ) { int nextDiff , lastDiff ; for ( int i = 0 ; i < size - 1 ; i ++ ) { nextDiff = pre [ i ] - pre [ i + 1 ] ; lastDiff = pre [ i ] - pre [ size - 1 ] ; if ( nextDiff * lastDiff < 0 ) { return false ; } ; } return true ; }