문제
Build an RNA string by replacing every DNA character with its partner. Use this complete mapping: A → U, C → G, G → C, T → A. Preserve the original order. No biology knowledge is needed.
Implement dna_to_rna(dna).
Input
dna: The DNA string to transform.
Output
Return the transformed string. Empty input returns an empty string.
제약 조건
0 ≤ DNA length ≤ 100,000. Characters are uppercase A, C, G, or T.
예시
입력:
dna = "ACGT"
예상 출력:
expected = "UGCA"입력:
std::string dna = "ACGT";
예상 출력:
std::string expected = "UGCA";입력:
string dna = "ACGT";
예상 출력:
string expected = "UGCA";설명
A becomes U, C becomes G, G becomes C, and T becomes A, giving UGCA.
입력:
dna = ""
예상 출력:
expected = ""입력:
std::string dna = "";
예상 출력:
std::string expected = "";입력:
string dna = "";
예상 출력:
string expected = "";설명
There are no characters to replace, so the result is empty.
접근 방법
먼저 스스로 풀어 본 뒤 힌트를 하나씩 열어 보세요.
힌트 1
Each DNA letter maps to exactly one RNA letter, so translate character by character.
힌트 2
Use a direct lookup for the four valid symbols while preserving the original order.
힌트 3
An empty input should return an empty string, and every character is guaranteed to be valid.
예상 복잡도
O(n) time, O(n) extra space
참고 자료
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