@topcoder.. You are correct.. I just figured out that the N<=3 condition is not always correct..
Below i have explained with example the code that will fix it: Basically for N=3 , say the sequence is a , b, c.. Then the valid cases would be: a < b < c a >= b >= c a < b , (b>=c and a < c) a >= b , ( b < c and c <= a) as u can see.. for 4, 2, 6 4 > 2 and ( 2 < 6 but 6 > 2) hence its invalid.. if ( A[0] < A[1] ) { if ( (A[1] < A[2]) ) { left = A[0]; mid = A[1]; right= A[2]; } else if (A[1] >= A[2] && A[0] < A[2] ) { left = A[0]; mid = A[2]; right = A[1]; } else goto end; printf("NO"); } else { if (A[1] >= A[2]) { left = A[2]; mid = A[1]; right = A[0]; } else if ( (A[1] < A[2]) && (A[0] >= A[2]) ) { left = A[1]; mid = A[2]; right = A[0]; } else goto end; printf("No"); } // Replace the greatest, smallest and mid code with the above one and it shall work.. On 30 Dec, 13:42, top coder <topcode...@gmail.com> wrote: > @Lucifer > > Looks like Your algo works for all of the my test cases. I am not able > to find counter case. > > Also we should not Print "Yes" for N<=3 > > For eg: > > A = 4,2,6 > > Then 2 is a root with 4 as left child and 6 as right child. It > contains two childs and fails the case. > > On Dec 30, 1:26 pm, Lucifer <sourabhd2...@gmail.com> wrote: > > > > > > > > > @above > > > Also i would like to mention that the above algo considers equal > > valued elements and assumes that the BST should have the following > > property: > > > 1) leftChild < = root > > 2) rightChild > root > > > On 30 Dec, 13:24, Lucifer <sourabhd2...@gmail.com> wrote: > > > > @An idea... > > > > Let the array of integers be A[N].. > > > > If N < = 3, then the answer would be YES. > > > > If N > 3, then the following algo will follow: > > > // The algo is self explanatory as its just ensuring BST property > > > keeping in mind that a parent node has only one child... > > > > int left = smallest(A[0], A[1], A[2]) ; > > > int right = greatest(A[0], A[1], A[2] ; > > > int mid = A[0] + A[1] + A[2] - left - right; > > > > int i = 2; > > > > while ( ++i < N) > > > { > > > if (A[i] <= mid && A[i] > left) > > > { > > > mid = A[i]; > > > right = mid; > > > } > > > else if (A[i] > mid && A[i] <= right) > > > { > > > mid = A[i]; > > > left = mid; > > > } > > > else > > > break; > > > > } > > > > if ( i == N) > > > printf ("YES"); > > > else > > > print("NO"); > > > > On 30 Dec, 12:51, top coder <topcode...@gmail.com> wrote: > > > > > Input : You have been given a sequence of integers. > > > > Now without actually constructing BST from the given sequence of > > > > integers (assuming the sequence is pre-order) determine if each node > > > > of BST has single child (either left or right but not both). > > > > Output : YES if given integer sequence corresponds to such a BST. > > > > otherwise say NO. > > > > > Ex. Say NO for 16,10,8,9,29,27,22. > > > > Say YES for 10,19,17,14,15,16 > > > > > I know the algo O(N^2) as follows: > > > > For every node in array(traverse from left to right), > > > > all the other nodes must be less or all the nodes must be greater > > > > than it. > > > > > But interviewer is expecting O(N). Any ideas?- Hide quoted text - > > > - Show quoted text - -- You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to algogeeks@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.