Array Index Safety - Problem

You are given an array of integers and a user-provided index. Your task is to safely access the array element at the given index and handle any out-of-bounds access gracefully.

Requirements:

If the index is valid (within array bounds), return the element at that index
If the index is out of bounds (negative or >= array length), return the string "Index out of bounds"
Use proper error handling techniques to catch and handle the exception

Note: This problem focuses on defensive programming and proper error handling when working with arrays.

Input & Output

Example 1 — Valid Index

$ Input: arr = [5,2,8,1], index = 2

› Output: 8

💡 Note: Index 2 is valid (within bounds 0-3), so return arr[2] = 8

Example 2 — Index Too Large

$ Input: arr = [5,2,8,1], index = 6

› Output: Index out of bounds

💡 Note: Index 6 is greater than array length 4, so return error message

Example 3 — Negative Index

$ Input: arr = [10,20,30], index = -1

› Output: Index out of bounds

💡 Note: Negative index -1 is invalid, so return error message

Constraints

1 ≤ arr.length ≤ 10⁴
-10⁹ ≤ arr[i] ≤ 10⁹
-10⁶ ≤ index ≤ 10⁶

Visualization

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Asked in

G Google 15 a Amazon 12 M Microsoft 10

The key insight is to validate array bounds before attempting access instead of relying on exception handling. The optimal approach uses boundary checking to prevent out-of-bounds errors. Time: O(1), Space: O(1)

Common Approaches

✓ Boundary Check First

⏱️ Time: O(1) Space: O(1)

This approach validates the index against array bounds before attempting access. If the index is valid, we access the element safely. If invalid, we immediately return an error message without triggering exceptions.

Try-Catch Exception Handling

⏱️ Time: O(1) Space: O(1)

This approach tries to access the array element directly and relies on the language's built-in exception handling to catch out-of-bounds errors. When an exception occurs, we catch it and return an error message.

Boundary Check First — Algorithm Steps

Step 1: Check if index is negative or >= array length
Step 2: If index is invalid, return error message immediately
Step 3: If index is valid, safely access and return arr[index]

Visualization

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Step-by-Step Walkthrough

Check Bounds

Validate index against array length

Early Return

Return error immediately if invalid

Safe Access

Access element only if index is valid

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* solution(int* arr, int arrSize, int index, char* result) {
    if (index < 0 || index >= arrSize) {
        strcpy(result, "Index out of bounds");
        return result;
    }
    sprintf(result, "%d", arr[index]);
    return result;
}

int main() {
    char line[1000];
    fgets(line, sizeof(line), stdin);
    
    // Parse array from JSON format
    int arr[100];
    int arrSize = 0;
    char* token = strtok(line + 1, ",]");
    while (token != NULL) {
        arr[arrSize++] = atoi(token);
        token = strtok(NULL, ",]");
    }
    
    int index;
    scanf("%d", &index);
    
    char result[100];
    solution(arr, arrSize, index, result);
    printf("%s\n", result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Single comparison and array access operations

✓ Linear Growth

Space Complexity

O(1)

No extra data structures needed

✓ Linear Space

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Array Index Safety - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Boundary Check First — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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