Google Interview Question for SDE1s


Country: United States




Comment hidden because of low score. Click to expand.
1
of 1 vote

pangram contains all letters of the alphabet Y. Palindrome reads the same forward and backwards.

Solution for palindrome is trivial, for every word find an inverse word or finding the inverse word missing the last character of the original word (even, odd palindrome) and minimize. If the words are in a dictionary it's O(n*m), n being the number of words, m being the average word length. How to imrpove: start with shorter words, needs some kind of order, use a trie (theoretically faster in constants, practically not due to cash misses)

For minimal pangram, the problem is a minimal cover set, I think it's called. It is known to be NP-hard. A greedy approach exists, that is not optimal, one takes the word with the most characters not already taken. This way the problem get's O(|Y|*n*m), Y is the alphabet, thus constant (e.g. 26), n is the number of words and m is the average word length. If we preprocess the words in O(n*m) we can get the algorithm down to O(|Y|^2*n) thus to O(n) for constant alphabet.

- Chris January 05, 2018 | Flag Reply
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0
of 0 vote

The solution I could think of is DFS on panagram part, keep a set on the on the string adding and reverse string comparing

- Anonymous January 15, 2018 | Flag Reply


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