Linear Search - Problem

Implement a linear search algorithm to find a specific element in an array.

Given an array of integers nums and a target value target, return the index of the target element if it exists in the array. If the target is not found, return -1.

Linear search checks each element in the array sequentially until it finds the target or reaches the end of the array.

Input & Output

Example 1 — Target Found

$ Input: nums = [4,7,2,9,1], target = 7

› Output: 1

💡 Note: The target 7 is found at index 1 in the array

Example 2 — Target Not Found

$ Input: nums = [1,3,5,7,9], target = 4

› Output: -1

💡 Note: The target 4 does not exist in the array, so return -1

Example 3 — Target at End

$ Input: nums = [2,4,6], target = 6

› Output: 2

💡 Note: The target 6 is found at the last index 2

Constraints

1 ≤ nums.length ≤ 10⁴
-10⁴ ≤ nums[i] ≤ 10⁴
-10⁴ ≤ target ≤ 10⁴

Visualization

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Asked in

G Google 25 a Amazon 30 M Microsoft 20 f Meta 15

Linear search is the simplest search algorithm that checks each element sequentially. The key insight is that for unsorted arrays, checking every element one by one is actually optimal. Best approach uses early termination when target is found. Time: O(n), Space: O(1)

Common Approaches

✓ Early Termination Linear Search

⏱️ Time: O(n) Space: O(1)

Same as basic linear search but emphasizes the optimization of returning immediately when the target is found, rather than continuing the search. This is the natural implementation but worth highlighting as an optimization concept.

Linear Search (Sequential Check)

⏱️ Time: O(n) Space: O(1)

Check each element in the array sequentially from left to right. When we find the target element, return its index immediately. If we finish checking all elements without finding the target, return -1.

Early Termination Linear Search — Algorithm Steps

Iterate through array elements
For each element, compare with target
Return index immediately when match found
Continue only if no match
Return -1 if entire array searched without finding target

Visualization

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Step-by-Step Walkthrough

Sequential check

Check elements one by one

Match found

Target found at index 1

Early return

Return immediately, skip remaining elements

Code -

solution.c — C

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

int solution(int* nums, int numsSize, int target) {
    for (int i = 0; i < numsSize; i++) {
        if (nums[i] == target) {
            return i; // Early termination
        }
    }
    return -1;
}

int main() {
    char line[1000];
    fgets(line, sizeof(line), stdin);
    
    // Parse array [1,2,3] format
    int nums[1000];
    int numsSize = 0;
    char* token = strtok(line + 1, ",]"); // Skip [
    while (token != NULL) {
        nums[numsSize++] = atoi(token);
        token = strtok(NULL, ",]");
    }
    
    int target;
    scanf("%d", &target);
    
    int result = solution(nums, numsSize, target);
    printf("%d\n", result);
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Best case O(1) if target is first element, worst case O(n) if target is last or not found

✓ Linear Growth

Space Complexity

O(1)

Only uses loop counter variable, no extra data structures

✓ Linear Space

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Linear Search - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Early Termination Linear Search — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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