Problem
Convert a score from 0 to 100 into a letter grade: 90 and above is A, 80–89 is B, 70–79 is C, 60–69 is D, and below 60 is F.
Implement letter_grade(score).
Input
score: The test score.
Output
Return the letter as a one-character string.
Constraints
0 ≤ score ≤ 100
Examples
Example 1
Input:
score = 85
Expected output:
expected = "B"Input:
long long score = 85;
Expected output:
std::string expected = "B";Input:
long score = 85;
Expected output:
string expected = "B";Explanation
85 is at least 80 but below 90, so the grade is B.
Example 2
Input:
score = 59
Expected output:
expected = "F"Input:
long long score = 59;
Expected output:
std::string expected = "F";Input:
long score = 59;
Expected output:
string expected = "F";Explanation
59 is below 60, so the grade is F.
How to approach it
Try on your own first, then open one hint at a time.
Hint 1
Compare the score against the highest passing threshold first and work downward.
Hint 2
A chain of ordered comparisons is the simplest way to map ranges to letters.
Hint 3
Make sure boundary scores like 90, 80, 70, and 60 fall into the higher grade band.
Expected complexity
O(1) time, O(1) extra space
References
This challenge is adapted for CodeUtility. Follow the statement and constraints above.