Things we will discuss here

  • Introduction
  • Linear Search Algorithm
  • Time and Space Complexity
  • C++ Implementation
  • Practice Problems


Linear search is a Search Algorithm as the name suggests. It is used on a collection of items. It relies on the technique of traversing a list from start to end by exploring the properties of all the elements that are found on the way.

Linear Search Algorithm

  • Take a collection of elements and let k (be the value to be searched for).
  • Now traverse (go through all the elements) the collection and check whether that element is equal to k or not.
    • If equal then print “Found” and break the loop.
    • Else go till the last element and if not found then print “Not Found”.

Example: Taking an array of 9 elements and searching for 4 in it.

Time and Space Complexity

Time Complexity

  • In this, in the worst case, we will be going to all the elements.
  • Hence the complexity is O(n) where n-number of elements in a collection.

Space Complexity

  • Here we need to store all the n elements in an array before searching so the space complexity it O(n).

C++ Implementation

#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;  // Number of element
    cin >> n;

    vector<int> arr(n);  // Declaring array of size n.
    for (int i = 0; i < n; i++) cin >> arr[i];

    int k;  // Number to be searched for in the array.
    cin >> k;

    bool found = false;  // found = true if number is present in array.
    for (int i = 0; i < n; i++) {
        if (arr[i] == k) {
            cout << "Found\n";
            found = true;

    // if number is not present.
    if (!found) {
        cout << "Not Found\n";

    return 0;

Input 1

1 2 3 4 5

Output 1


Input 2

1 2 3 4 5

Output 2

Not Found

Practice Problems

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