Watch 10 video solutions for Count Unique Characters of All Substrings of a Given String, a hard level problem involving Hash Table, String, Dynamic Programming. This walkthrough by NeetCode has 657,697 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
Let's define a function countUniqueChars(s) that returns the number of unique characters in s.
countUniqueChars(s) if s = "LEETCODE" then "L", "T", "C", "O", "D" are the unique characters since they appear only once in s, therefore countUniqueChars(s) = 5.Given a string s, return the sum of countUniqueChars(t) where t is a substring of s. The test cases are generated such that the answer fits in a 32-bit integer.
Notice that some substrings can be repeated so in this case you have to count the repeated ones too.
Example 1:
Input: s = "ABC" Output: 10 Explanation: All possible substrings are: "A","B","C","AB","BC" and "ABC". Every substring is composed with only unique letters. Sum of lengths of all substring is 1 + 1 + 1 + 2 + 2 + 3 = 10
Example 2:
Input: s = "ABA"
Output: 8
Explanation: The same as example 1, except countUniqueChars("ABA") = 1.
Example 3:
Input: s = "LEETCODE" Output: 92
Constraints:
1 <= s.length <= 105s consists of uppercase English letters only.