3043. Find the Length of the Longest Common Prefix

Problem Link

Description

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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

Solution

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Python3

class Solution:
    def longestCommonPrefix(self, arr1: List[int], arr2: List[int]) -> int:
        N, M = len(arr1), len(arr2)
        res = 0
        mp1 = set()
        
        for x in arr1:
            s = str(x)
            curr = ""
            
            for c in s:
                curr += c
                mp1.add(curr)
        
        for x in arr2:
            s = str(x)
            
            for k in range(len(s)):
                if s[0 : len(s) - k] in mp1:
                    res = max(res, len(s) - k)
        
        
        return res