Grade Classifier - Problem

You are building a grading system for a school. Given a student's numerical score (0-100), you need to assign the corresponding letter grade based on the standard grading scale.

Grading Scale:

A: 90-100
B: 80-89
C: 70-79
D: 60-69
F: 0-59

Your task is to write a function that takes a numerical score and returns the appropriate letter grade as a string.

Input & Output

Example 1 — Excellent Grade

$ Input: score = 92

› Output: A

💡 Note: Score 92 is >= 90, so it falls in the A grade range (90-100)

Example 2 — Good Grade

$ Input: score = 85

› Output: B

💡 Note: Score 85 is >= 80 but < 90, so it gets grade B (80-89)

Example 3 — Failing Grade

$ Input: score = 45

› Output: F

💡 Note: Score 45 is < 60, so it receives the failing grade F

Constraints

0 ≤ score ≤ 100
Score is always an integer

Visualization

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Asked in

a Amazon 15 M Microsoft 12 G Google 8

The key insight is to use an if-else ladder starting from the highest grade range and working downward. This allows early termination once a condition is met. Best approach uses connected if-else structure: Time: O(1), Space: O(1)

Common Approaches

✓ If-Else Ladder (Optimized)

⏱️ Time: O(1) Space: O(1)

Use a connected if-else if structure that starts checking from the highest grade (A) and stops immediately once a condition is met, avoiding unnecessary checks.

Multiple If-Else Chain

⏱️ Time: O(1) Space: O(1)

Use a series of independent if-else statements to check each grade range from lowest to highest, evaluating all conditions even when a match is found early.

If-Else Ladder (Optimized) — Algorithm Steps

Check if score >= 90, return A
Else if score >= 80, return B
Continue with else-if chain
Default case returns F

Visualization

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Step-by-Step Walkthrough

Check Highest

Start with score >= 90

Early Exit

Stop when condition matches

Result

Return grade immediately

Code -

solution.c — C

#include <stdio.h>

char* solution(int score) {
    if (score >= 90) {
        return "A";
    } else if (score >= 80) {
        return "B";
    } else if (score >= 70) {
        return "C";
    } else if (score >= 60) {
        return "D";
    } else {
        return "F";
    }
}

int main() {
    int score;
    scanf("%d", &score);
    char* result = solution(score);
    printf("%s\n", result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

At most 4 comparisons needed, constant time

✓ Linear Growth

Space Complexity

O(1)

Only uses local variables, no additional memory

✓ Linear Space

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Grade Classifier - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

If-Else Ladder (Optimized) — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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