Python - Elements Maximum till current index in List

Python – Elements Maximum till current index in List

Last Updated : 01 Aug, 2020

Given list with elements, extract element if it’s the maximum element till current index.

Input : test_list = [4, 6, 7, 8]
Output : [4, 6, 7, 8]
Explanation : All elements are maximum till their index.
Input : test_list = [6, 7, 3, 6, 8, 7]

Output : [7, 8]
Explanation : 7 and 8 are maximum till their index.

Method #1 : Using loop

This is brute method in which this task can be performed. In this, we run nested loop till current index and increment the counter if all elements are lower than current element, if counter matches the current index, suggests that current element is maximum till current index.

Python3

# Python3 code to demonstrate working of
# Elements Maximum till current index in List
# Using loop
  
# initializing list
test_list = [3, 5, 2, 6, 7, 9, 3]
  
# printing original list
print("The original list : " + str(test_list))
  
# Using loop
res = []
for idx in range(1, len(test_list)):
    cnt = 0
  
    # inner loop to count element less than current
    for idx2 in range(idx):
        if test_list[idx] > test_list[idx2]:
            cnt = cnt + 1
    if cnt == idx:
        res.append(test_list[idx])
  
# printing result
print("Extracted Maximum elements : " + str(res))

Output

The original list : [3, 5, 2, 6, 7, 9, 3]
Extracted Maximum elements : [5, 6, 7, 9]

Method #2 : Using max() + list comprehension + list slicing

The combination of above functions can be used to solve this problem. In this, we use max() to check if current element is greater that all previous elements extracted using list slicing.

Python3

# Python3 code to demonstrate working of
# Elements Maximum till current index in List
# Using max() + list comprehension + list slicing
  
# initializing list
test_list = [3, 5, 2, 6, 7, 9, 3]
  
# printing original list
print("The original list : " + str(test_list))
  
# Using max() + list comprehension + list slicing
# max() used to get if current is current maximum
res = [test_list[idx] for idx in range(
    1, len(test_list)) if test_list[idx] > max(test_list[:idx])]
  
# printing result
print("Extracted Maximum elements : " + str(res))

Output

The original list : [3, 5, 2, 6, 7, 9, 3]
Extracted Maximum elements : [5, 6, 7, 9]

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