# Program to find length of longest sublist whose sum is 0 in Python

Suppose we have a list with only two values 1 and −1. We have to find the length of the longest sublist whose sum is 0.

So, if the input is like nums = [1, 1, −1, 1, 1, −1, 1, −1, 1, −1], then the output will be 8, as the longest sublist is [−1, 1, 1, −1, 1, −1, 1, −1] whose sum is 0.

To solve this, we will follow these steps −

• table := a new empty map

• cs := 0, max_diff := 0

• for i in range 0 to size of nums − 1, do

• cs := cs + nums[i]

• if cs is same as 0, then

• max_diff := maximum of i + 1 and max_diff

• if cs is in table, then

• max_diff := maximum of max_diff and (i − table[cs])

• otherwise,

• table[cs] := i

• return max_diff

Let us see the following implementation to get better understanding −

## Example

Live Demo

class Solution:
def solve(self, nums):
table = {}
cs = 0
max_diff = 0
for i in range(len(nums)):
cs += nums[i]
if cs == 0:
max_diff = max(i + 1, max_diff)
if cs in table:
max_diff = max(max_diff, i − table[cs])
else:
table[cs] = i
return max_diff
ob = Solution()
nums = [1, 1, −1, 1, 1, −1, 1, −1, 1, −1]
print(ob.solve(nums))

## Input

[1, 1, −1, 1, 1, −1, 1, −1, 1, −1]

## Output

8