Mothesh-M127 / Search-Algorithm

Linear Search and Binary search

Linear Search and Binary search

Aim:

To write a program to perform linear search and binary search using python programming.

Equipment’s required:

1. Hardware – PCs
2. Anaconda – Python 3.7 Installation / Moodle-Code Runner

Algorithm:

Linear Search:

1. Start from the leftmost element of array[] and compare k with each element of array[] one by one.
2. If k matches with an element in array[] , return the index.
3. If k doesn’t match with any of elements in array[], return -1 or element not found.

Binary Search:

1. Set two pointers low and high at the lowest and the highest positions respectively.
2. Find the middle element mid of the array ie. arr[(low + high)/2]
3. If x == mid, then return mid.Else, compare the element to be searched with m.
4. If x > mid, compare x with the middle element of the elements on the right side of mid. This is done by setting low to low = mid + 1.
5. Else, compare x with the middle element of the elements on the left side of mid. This is done by setting high to high = mid - 1.
6. Repeat steps 2 to 5 until low meets high

Program:

i) #Use a linear search method to match the item in a list.

def linearSearch(array,n,k):
    # write your code for linear search
    for i in range(0,n):
        if array[i]==k:
            return i
    return -1      
    
array = eval(input())
array.sort()
k = eval(input()) 
n=len(array)
result = linearSearch(array,n,k)
if result >=0:
    print(array)
    print('Element found at index: ',result)
else:
    print(array)
    print('Element not found')

ii) # Find the element in a list using Binary Search(Iterative Method).

def binarySearchIter(array, k, low, high):
    while(low<=high):
        mid=low+(high-low)//2
        if array[mid]==k:
            return mid
        elif array[mid]<k:
            low=mid+1
        else:
            high=mid+1
    return -1
array=eval(input())
#sort the array
array.sort()
print(array)
#k-item to be searched
k=eval(input()) 
low=0
high= len(array)-1
# use the binary search function to find the item in the list
result=binarySearchIter(array, k, low, high)
# use if-else to print sorted array and "Element not found" if the item is not present in the list otherwise print sorted array and "Element found at index: ", result
if result>=0:
    print("Element found at index: ",result)
else:
    print("Element not found")

iii) # Find the element in a list using Binary Search (recursive Method).

def BinarySearch(arr, k, low, high):
    if high>=low:
        mid=low+(high-low)//2
        if arr[mid]==k:
            return mid
        elif arr[mid]<k:
            return BinarySearch(arr,k,mid+1,high)
        else:
            return BinarySearch(arr,k,low,mid+1)
    return -1
arr = eval(input())
#sort the array
arr.sort()
print(arr)
# k is the element to be searched for
k = eval(input()) 
low=0
high=len(arr)-1
# use the binary search function to find the result
result=BinarySearch(arr, k, low, high)
# use if-else to print sorted array and "Element not found" if the item is not present in the list otherwise print sorted array and "Element found at index: ", result
if result>=0:
    print("Element found at index: ",result)
else:
    print("Element not found")

Sample Input and Output

output1:

output2:

output3:

Result

Thus the linear search and binary search algorithm is implemented using python programming.