Problem
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 a common prefix 565 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 * 1041 <= arr1[i], arr2[i] <= 108
Solution
/**
* @param {number[]} arr1
* @param {number[]} arr2
* @return {number}
*/
var longestCommonPrefix = function(arr1, arr2) {
var trie = {};
for (var i = 0; i < arr1.length; i++) {
var str = `${arr1[i]}`;
var map = trie;
for (var j = 0; j < str.length; j++) {
if (!map[str[j]]) {
map[str[j]] = {};
}
map = map[str[j]];
}
}
var max = 0;
for (var i = 0; i < arr2.length; i++) {
var str = `${arr2[i]}`;
var map = trie;
var len = 0;
for (var j = 0; j < str.length; j++) {
if (!map[str[j]]) {
break;
}
len += 1;
map = map[str[j]];
}
max = Math.max(max, len);
}
return max;
};
Explain:
Trie.
Complexity:
- Time complexity : O(n * m).
- Space complexity : O(n * m).