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 a 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 the elements, return -1.
Example: 
Iterative Approach:
Python
# 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 -1def search(arr, x): for i in range(len(arr)): if arr[i] == x: return i return -1 |
Recursive Approach:
Python
# This is similar to the above one, with the only difference# being that it is using the recursive approach instead of iterative.def search(arr, curr_index, key): if curr_index == -1: return -1 if arr[curr_index] == key: return curr_index return search(arr, curr_index-1, key) |
The time complexity of the above algorithm is O(n).
Auxiliary Space: O(1) for iterative and O(n) for recursive.
Please refer complete article on Linear Search and Difference Between Recursive and Iterative Algorithms for more details!
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