Quora haqathon 2014

Quora haqathon today, from 11am to 7pm - Pacific standard time! Features 9 problems mixed with tradition algorithm tasks, machine learning and system programming tasks.  Link to site.

Ontology
Linearize the tree - each query reduces to "in question q[x...y], how many of them start with prefix p?". Offline query + Partial Sum + Trie. Linear time.

Wombats
Maximum closure.

Labeler
Use training set to calculate $\text{Pr}[q_i \in t_k | w_j \in q_i ]$ for all question $q_i$, topic $t_k$ and word $w_j$. Improve using bi-gram.

Duplicate
Use $\text{Pr}[w \in \text{question_text}_i \text{ and } w \notin \text{question_text}_j ]$ as classifying criteria - 60% accuracy. Consider also $\frac{\text{view_count}_i }{ \text{view_count}_j }$ improved it to 70%.