OpenText Software Engineer interview questions

1.Implement queue using two stack (famous interview question) 2.find the anagrams maximum count {"aab", "baa","aba","abc"} that he was asking me to order of n. I have suggested different algo like Trie ,wordMap ,etc but he asked me to algo in o(n) ,i don't think so possible .if somebody know in o(n) share the code with me. 3.given array {10,20,12,10,18,2} etc find the sum of two element 20. 4.find the given no in binary tree ---my answer is level order traversal ..but he doesn't understand he want different solution. 5.continous data stream find the given word ...i have suggested maximum heap implementation and trie