# Python program to find the Decreasing point in List

• Last Updated : 12 Nov, 2020

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 list``test_list ``=` `[``3``, ``6``, ``8``, ``9``, ``12``, ``5``, ``18``, ``1``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `res ``=` `-``1``for` `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 list``test_list ``=` `[``3``, ``6``, ``8``, ``9``, ``12``, ``5``, ``18``, ``1``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `res ``=` `-``1``for` `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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