Table of Contents
What is Linear Search?
In Linear Search, we sequentially iterate over the given list and check if the element we are looking for is equal to the one in the list. Some quick points about Linear Search.
- A simple and easy to implement searching technique
- Used when elements in the list are not sorted.
- Inefficient technique compared to Binary Search
Let’s take a look at the following code;
Analysis of the above code:
- We pass the element we are looking for and the list to search in to
- In the function
linear_search(), we loop over the length of the
search_listand see if the current element equals the element being searched.
- If that condition evaluated to
Truethen we return the value of
- Else, in the end, when the loop breaks, we return -1
What is Bisection/Binary Search?
Binary Search or Bisection Search or Logarithmic Search is a search algorithm that finds the position/index of an element within a sorted search list. Quick points about binary search.
- Can only be used when the list is sorted (we can sort the list if our list is not already sorted)
- Efficient technique compared to Linear Search
Let’s first understand the concept of Binary Search before getting into implementation details.
Let’s say that we have to search the index of
[4, 8, 9, 10, 24, 32, 45, 56]
- Look for the middle element in the list. It is
- Compare that middle element with
24is less than
- This means that all the numbers on the left of
24are less than
24and there’s no point of searching for
32in that part of the list.
- So we will look in the right half of
- Now, our list looks like this. [
4, 8, 9, 10, 24,32, 45, 56].
- Again, look for the middle element,
45 > 32. So no point in looking at elements in the right half of
- Now the list has broken down to [
4, 8, 9, 10, 24,32, 45, 56], the only element left is
32. we have found what we were looking for.
Let’s implement that in code.
Notice the number of iterations required in binary search compared to linear search. When the list if really large, binary search proves to be way more efficient compared to linear search.
Points to note between Linear Search & Bisection Search:
- Note that we cut down the list in half each time we compare 32 with any element, while in Linear Search we kept on searching through whole list. Hence Bisection Search is way better than Linear Search.
- There is technical term to denote efficiency, ‘Time Complexity’, and represented as O()
- Time Complexity of Linear Search is O(n), where n is the number of elements in the list.
- Time Complexity of Bisection Search is O(log n). We will see more about Time Complexity in future.
We make use of the concept of Binary Search to find square root of a number in an efficient way.
Note: This is a part of what I learned in an online Open Course Ware offered by MIT on edX. Its for my personal reference & also for those who would like to revisit the course.