1239.Maximum Length of a Concatenated String with Unique Characters
Description:
Given an array of strings arr
. String s
is a concatenation of a subsequence of arr
which have unique characters.
Return the maximum possible length of s
.
Sample Input:
1  Input: arr = ["un","iq","ue"] 
1  Input: arr = ["abcdefghijklmnopqrstuvwxyz"] 
Constraints:
1 <= arr.length <= 16
1 <= arr[i].length <= 26
arr[i]
contains only lower case English letters.
Note:
A subsequence should preserve the order.
 For example, arr = [“un”,”iq”,”ue”], “iqun” is not a valid answer.
 Corollary:
 However, we only want the length of the string, so the order of the strings are trivial.
The constraints has implied us that the algorithm could be exponential.
if arr[i] itself contains duplicate characters, it’s invalid.
BruteForce:
Traverse all the string pair, find if the concantenated string has duplicate char.
Time Complexity $O(2^n)$ : each string can be cancatenated or not.
Technique:
Since the arr[i].length<=26<32, we can use a 32bit int to do the char count
(How many times each character present in a string instead of map)
Time Complexity $O(2^n)$ : each string can be cancatenated or not.
Space Complexity $O(n)$ : using DFS recursion, the space complexity equals to the depth of recursion.
Sample:
Referenced from Hua Hua@Youtube
Code
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