# Program to check all 1s are present one after another or not in Python

PythonServer Side ProgrammingProgramming

#### Beyond Basic Programming - Intermediate Python

Most Popular

36 Lectures 3 hours

#### Practical Machine Learning using Python

Best Seller

91 Lectures 23.5 hours

#### Practical Data Science using Python

22 Lectures 6 hours

Suppose we have a list of numbers called nums that contains at least one element whose value is 1. We have to check whether all the 1s appear consecutively or not.

So, if the input is like nums = [8, 2, 1, 1, 1, 3, 5], then the output will be True.

To solve this, we will follow these steps −

• visited := 0

• for each x in nums, do

• if x is same as 1, then

• if visited is same as 2, then

• return False

• visited := 1

• otherwise when visited is non-zero, then

• visited := 2

• return True

## Example

Let us see the following implementation to get better understanding

def solve(nums):
visited = 0
for x in nums:
if x == 1:
if visited == 2:
return False
visited = 1
elif visited:
visited = 2
return True

nums = [8, 2, 1, 1, 1, 3, 5]
print(solve(nums))

## Input

[8, 2, 1, 1, 1, 3, 5]


## Output

True