Given a list, write a Python program to check if all the elements in the given list are the same.
Example:
Input: ['Geeks', 'Geeks', 'Geeks', 'Geeks', ] Output: Yes
Input: ['Geeks', 'Is', 'all', 'Same', ] Output: No
There are various ways we can do this task. Let’s see different ways we can check if all elements in a List are the same.
Method #1: Comparing each element.
Python3
# Python program to check if all# elements in a List are samedef checkList(lst): ele = lst[0] chk = True # Comparing each element with first item for item in lst: if ele != item: chk = False break if (chk == True): print("Equal") else: print("Not equal")# Driver Codelst = ['Geeks', 'Geeks', 'Geeks', 'Geeks', ]checkList(lst) |
Equal
But In Python, we can do the same task in many interesting ways.
Method #2: Using all() method
Python3
# Python program to check if all# elements in a List are sameres = Falsedef chkList(lst): if len(lst) < 0: res = True res = all(ele == lst[0] for ele in lst) if(res): print("Equal") else: print("Not equal")# Driver Codelst = ['Geeks', 'Geeks', 'Geeks', 'Geeks']chkList(lst) |
Equal
Method #3: Using count() method
Python3
# Python program to check if all# elements in a List are sameres = Falsedef chkList(lst): if len(lst) < 0: res = True res = lst.count(lst[0]) == len(lst) if(res): print("Equal") else: print("Not equal")# Driver Codelst = ['Geeks', 'Geeks', 'Geeks', 'Geeks']chkList(lst) |
Equal
Method #4: Using set data structure Since we know there cannot be duplicate elements in a set, we can use this property to check whether all the elements are same or not.
Python3
# Python program to check if all# elements in a List are samedef chkList(lst): return len(set(lst)) == 1# Driver Codelst = ['Geeks', 'Geeks', 'Geeks', 'Geeks']if chkList(lst) == True: print("Equal")else: print("Not Equal") |
Equal
Method #5 : Using len() method
Python3
# Python program to check if all# elements in a List are samelst = ['Geeks', 'Geeks', 'Geeks', 'Geeks']if([lst[0]]*len(lst) == lst): print("Equal")else: print("Not equal") |
Equal
Method#6: Using recursion
Python3
#Python program to check if all the elements in the given list are the same.def checkList(lst, ele=None, index=0): # if ele is None, assign the first element of the list to ele if ele is None: ele = lst[0] # base case: if index is equal to the length of the list, return True if index == len(lst): return True # if the current element at index is not equal to ele, return False elif lst[index] != ele: return False # otherwise, call the function again with the next index else: return checkList(lst, ele, index+1)# Driver Codelst = ['Geeks', 'Geeks', 'Geeks', 'Geeks']# check if the function returns Trueif checkList(lst): print("Equal")else: print("Not equal")#This code is contributed Vinay Pinjala. |
Equal
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #7: Using the reduce function from the functools library and the operator module:
Python3
from functools import reduceimport operatordef all_elements_same(lst): return reduce(operator.eq, lst)# driver codelst = [1,1,1,1,1]if all_elements_same(lst): print("Equal")else: print("Not Equal") |
Output:
Equal
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #8 : Using operator.countOf() method
- Check whether count of first element is equal to length of list using operator.countOf()
- If True then all elements of list are equal Display Equal
- If False then Display Not equal
Python3
# Python program to check if all# elements in a List are sameimport operatorres = Falsedef chkList(lst): if len(lst) < 0: res = True res = operator.countOf(lst, lst[0]) == len(lst) if(res): print("Equal") else: print("Not equal")# Driver Codelst = ['Geeks', 'Geeks', 'Geeks', 'Geeks']chkList(lst) |
Equal
Time Complexity: O(n) n – length of list
Auxiliary Space: O(1)
Method #9: Using heapq module:
- Import the heapq module.
- Define the all_elements_same function which takes a list as an argument.
- Use the nsmallest function from heapq to find the smallest len(lst) elements in the list and check if all the elements found are equal to the first element of the list using all() functions. If it is True, print “Equal“, else print “Not Equal“.
Below is the implementation of the above approach:
Python3
# Python program for the above approachimport heapq# Function to check if all elements# are same or notdef all_elements_same(lst): return all(x == lst[0] for x in heapq.nsmallest(len(lst), lst))# Driver Codelst = [1, 1, 1, 1, 1]if all_elements_same(lst): print("Equal")else: print("Not Equal")# This code is contributed by Rayudu |
Equal
Time Complexity: The time complexity of this algorithm is O(N log N), where N is the length of the input list. This is because the nsmallest function uses a heap to find the smallest elements, which has a time complexity of O(N log N).
Space Complexity: The space complexity of this algorithm is O(N), where N is the length of the input list. This is because the nsmallest function creates a heap of size n to store the smallest elements. Additionally, the generator expression used in all functions also requires O(N) space.
