Python Program for Linear Search

Problem: Given an array arr[] of n elements, write a function to search a given element x in arr[].
Examples :

Input : arr[] = {10, 20, 80, 30, 60, 50, 
                     110, 100, 130, 170}
          x = 110;
Output : 6
Element x is present at index 6

Input : arr[] = {10, 20, 80, 30, 60, 50, 
                     110, 100, 130, 170}
           x = 175;
Output : -1
Element x is not present in arr[].

A simple approach is to do linear search, i.e

  • Start from the leftmost element of arr[] and one by one compare x with each element of arr[]
  • If x matches with an element, return the index.
  • If x doesn’t match with any of elements, return -1.


Example:
linear-search1



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# Searching an element in a list/array in python
# can be simply done using \'in\' operator
# Example:
# if x in arr:
#   print arr.index(x)
  
# If you want to implement Linear Search in python
  
# Linearly search x in arr[]
# If x is present then return its location
# else return -1
  
def search(arr, x):
  
    for i in range(len(arr)):
  
        if arr[i] == x:
            return i
  
    return -1

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The time complexity of above algorithm is O(n).

Please refer complete article on Linear Search for more details!



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