First Unique Character

Problème

Return the index of the first character in text that appears exactly once. Case matters.

Implement first_unique_index(text).

text: The text to inspect.

Return the index, or -1 if every character repeats.

0 ≤ length ≤ 100,000

Exemple 1

Entrée :
text = "swiss"

Sortie attendue :
expected = 1

Entrée :
std::string text = "swiss";

Sortie attendue :
long long expected = 1;

Entrée :
string text = "swiss";

Sortie attendue :
long expected = 1;

s repeats, w appears once at index 1.

Exemple 2

Entrée :
text = "aabb"

Sortie attendue :
expected = -1

Entrée :
std::string text = "aabb";

Sortie attendue :
long long expected = -1;

Entrée :
string text = "aabb";

Sortie attendue :
long expected = -1;

Every character repeats: -1.

Essayez d'abord seul, puis ouvrez les indices un par un.

Indice 1

You need characters that appear exactly once, not just the first different one.

Indice 2

Count all character frequencies first, then find the earliest position with frequency one.

Indice 3

Remember that uppercase and lowercase letters are different characters.

Complexité attendue

O(n) time, O(k) extra space

Ce défi a été adapté pour CodeUtility. Suivez l'énoncé et les contraintes ci-dessus.