- Difficulty: Hard
- Tags: LeetCode, Hard, Bit Manipulation, Array, Hash Table, String, Enumeration, leetcode-2306, O(26 * n * l), O(n * l), Math
Problem
You are given an array of strings ideas
that represents a list of names to be used in the process of naming a company. The process of naming a company is as follows:
- Choose 2 distinct names from
ideas
, call themideaA
andideaB
. - Swap the first letters of
ideaA
andideaB
with each other. - If both of the new names are not found in the original
ideas
, then the nameideaA ideaB
(the concatenation ofideaA
andideaB
, separated by a space) is a valid company name. - Otherwise, it is not a valid name.
Return the number of distinct valid names for the company.
Example 1:
Input: ideas = ["coffee","donuts","time","toffee"] Output: 6 Explanation: The following selections are valid: - ("coffee", "donuts"): The company name created is "doffee conuts". - ("donuts", "coffee"): The company name created is "conuts doffee". - ("donuts", "time"): The company name created is "tonuts dime". - ("donuts", "toffee"): The company name created is "tonuts doffee". - ("time", "donuts"): The company name created is "dime tonuts". - ("toffee", "donuts"): The company name created is "doffee tonuts". Therefore, there are a total of 6 distinct company names. The following are some examples of invalid selections: - ("coffee", "time"): The name "toffee" formed after swapping already exists in the original array. - ("time", "toffee"): Both names are still the same after swapping and exist in the original array. - ("coffee", "toffee"): Both names formed after swapping already exist in the original array.
Example 2:
Input: ideas = ["lack","back"] Output: 0 Explanation: There are no valid selections. Therefore, 0 is returned.
Constraints:
2 <= ideas.length <= 5 * 104
1 <= ideas[i].length <= 10
ideas[i]
consists of lowercase English letters.- All the strings in
ideas
are unique.