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  1. Maximum Xor
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Maximum Xor

  • nonchalant_enth1
     + 0 comments

    Python solution O(30*n+30*m) - time, O(30*n) - space for the trie of bits prefixes:

    def maxXor(arr, queries):
    trie = dict()
    cur = trie
    #build a trie of numbers' bits prefixes
    for a in arr:
        for bit in map(int, bin(a)[2:].zfill(30)):
            if bit not in cur:
                cur[bit] = {}
            cur = cur[bit]
        cur = trie
    
    rez = []
    #given a trie of bits prefixes and a query, do a greedy search on it
    for q in queries:
        sub_rez = ''
        for bit in map(int, bin(q)[2:].zfill(30)):
            if 1 - bit in cur:
                sub_rez += '1'
                cur = cur[1 - bit]
            else:
                sub_rez += '0'
                cur = cur[bit]
        rez.append(int(sub_rez, 2))
        cur = trie
    return rez