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3329. Find The Length Of The Longest Common Prefix

Array Hash Table String Trie

Problem - Find The Length Of The Longest Common Prefix

Medium

You are given two arrays with positive integers arr1 and arr2.

A prefix of a positive integer is an integer formed by one or more of its digits, starting from its leftmost digit. For example, 123 is a prefix of the integer 12345, while 234 is not.

A common prefix of two integers a and b is an integer c, such that c is a prefix of both a and b. For example, 5655359 and 56554 have common prefixes 565 and 5655 while 1223 and 43456 do not have a common prefix.

You need to find the length of the longest common prefix between all pairs of integers (x, y) such that x belongs to arr1 and y belongs to arr2.

Return the length of the longest common prefix among all pairs. If no common prefix exists among them, return 0.

 

Example 1:

Input: arr1 = [1,10,100], arr2 = [1000]
Output: 3
Explanation: There are 3 pairs (arr1[i], arr2[j]):
- The longest common prefix of (1, 1000) is 1.
- The longest common prefix of (10, 1000) is 10.
- The longest common prefix of (100, 1000) is 100.
The longest common prefix is 100 with a length of 3.

Example 2:

Input: arr1 = [1,2,3], arr2 = [4,4,4]
Output: 0
Explanation: There exists no common prefix for any pair (arr1[i], arr2[j]), hence we return 0.
Note that common prefixes between elements of the same array do not count.

 

Constraints:

  • 1 <= arr1.length, arr2.length <= 5 * 104
  • 1 <= arr1[i], arr2[i] <= 108

Solutions

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class Solution:
    def longestCommonPrefix(self, arr1: List[int], arr2: List[int]) -> int:
        set_vals = set()
        for val in arr1:
            while val:
                set_vals.add(val)
                val //= 10

        result = 0
        for val in arr2:
            while val:
                if val in set_vals:
                    result = max(result, len(str(val)))
                    break
                val //= 10

        return result

Submission Stats:

  • Runtime: 206 ms (79.27%)
  • Memory: 28.8 MB (78.62%)