def max_sum_non_adjacent(arr): if not arr: return 0 if len(arr) == 1: return arr[0]

# Initialize prev2 (max sum until i-2) and prev1 (max sum until i-1)
prev2 = 0
prev1 = 0

# Traverse through the array
for num in arr:
    current = max(prev1, num + prev2)
    prev2 = prev1
    prev1 = current

return prev1