Problème
Compare two DNA strings position by position and count the differences. Only characters at the same position are compared; do not insert, delete, or shift characters. No biology knowledge is needed.
Implement hamming_distance(first, second).
Input
first: The first DNA string.
second: The equal-length second DNA string.
Output
Return the number of positions with different characters.
Contraintes
Both strings have the same length, from 0 to 100,000. Characters are uppercase A, C, G, or T.
Exemples
Entrée :
first = "ACCT"
second = "AGCA"
Sortie attendue :
expected = 2Entrée :
std::string first = "ACCT";
std::string second = "AGCA";
Sortie attendue :
long long expected = 2;Entrée :
string first = "ACCT";
string second = "AGCA";
Sortie attendue :
long expected = 2;Explication
The second position is C versus G and the fourth is T versus A. The first and third match: two differences.
Entrée :
first = "GATT"
second = "GATT"
Sortie attendue :
expected = 0Entrée :
std::string first = "GATT";
std::string second = "GATT";
Sortie attendue :
long long expected = 0;Entrée :
string first = "GATT";
string second = "GATT";
Sortie attendue :
long expected = 0;Explication
All four positions match, so no differences are counted.
Comment l'aborder
Essayez d'abord seul, puis ouvrez les indices un par un.
Indice 1
Compare both strings one position at a time and count when the characters differ.
Indice 2
A single pass with paired iteration is enough; no rearranging or substring searches are needed.
Indice 3
Remember that equal-length inputs can still be empty, which should yield zero differences.
Complexité attendue
O(n) time, O(1) extra space
Références
Ce défi a été adapté pour CodeUtility. Suivez l'énoncé et les contraintes ci-dessus.