Python program to find the Decreasing point in List
Given a list, get the index of element where the list shows the first negative trend, i.e first point where the next element < current element. If not found return -1.
Input : test_list = [3, 6, 8, 9, 12, 5, 18, 1]
Output : 4
Explanation : At 12 -> 5, first decreasing point occurs.Input : test_list = [3, 9, 12, 5, 18, 1]
Output : 2
Explanation : At 12 -> 5, first decreasing point occurs.
Method #1 : Using loop
In this, we check for the next element to be less than the current element, at a point where it is first found, we break the loop.
Python3
# Python3 code to demonstrate working of # Decreasing point in List# Using loop # initializing listtest_list = [3, 6, 8, 9, 12, 5, 18, 1] # printing original listprint("The original list is : " + str(test_list)) res = -1for idx in range(0, len(test_list) - 1): # checking for 1st decreasing element if test_list[idx + 1] < test_list[idx]: res = idx break # printing result print("Decreasing Point : " + str(res)) |
Output:
The original list is : [3, 6, 8, 9, 12, 5, 18, 1] Decreasing Point : 4
Method #2 : Using enumerate() + loop
In this, we check for index and value simultaneously using enumerate, a similar method to above, the difference being separate index element access.
Python3
# Python3 code to demonstrate working of # Decreasing point in List# Using enumerate() + loop # initializing listtest_list = [3, 6, 8, 9, 12, 5, 18, 1] # printing original listprint("The original list is : " + str(test_list)) res = -1for idx, ele in enumerate(test_list): # checking for 1st decreasing element if test_list[idx + 1] < ele: res = idx break # printing result print("Decreasing Point : " + str(res)) |
Output:
The original list is : [3, 6, 8, 9, 12, 5, 18, 1] Decreasing Point : 4
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