This challenge is the easiest one I encountered on this season. And I was able to find a working algorithm. Still I am not even on top 7k. I started with copying test example and pasting on `day9_test.txt`

and my input on `day9.txt`

both are at same directory as my notebook is.

Lets share your solution too.

## Challenge 1

```
with open("day9.txt", "r") as fp:
lines = [int(line.rstrip()) for line in fp.readlines()]
# lines
def challenge1(codes, premable):
previous_stack = []
i = 0
start = 0
end = start+premable
curr_index = premable
while curr_index < len(codes)-1:
stack = codes[start:end]
if curr_index > len(stack)-1:
start+=1
end+=1
valid = False
for i in stack[:-1]:
for j in stack[1:]:
#print(codes[curr_index], i, j)
if i+j == codes[curr_index]:
valid = True
break
else:
valid == False
if valid:
break
if valid == False:
return codes[curr_index]
curr_index+=1
# print(stack)
# break
challenge1(lines, 25)
```

## Challenge 2

Used NumPy for taking sum faster.

```
import numpy as np
def challenge2(codes, invalid_num):
contigous_list = []
for i in range(0, len(codes)-1):
for j in range(1, len(codes)-1):
stack = np.array(codes[i:j])
if np.sum(stack) == invalid_num:
print(stack, stack.min()+stack.max())
# print(stack)
challenge2(lines, challenge1(lines, 25))
```

I write blogs about Computer Vision projects on my GitHub page q-viper.github.io and if you got some time please share yours too.

## Top comments (1)

It is so neat an clear. Thank you for sharing.