Program to find length of longest sublist containing repeated numbers by k operations in Python

Suppose we have a list called nums and a value k, now let us consider an operation by which we can update the value of any number in the list. We have to find the length of the longest sublist which contains repeated numbers after performing at most k operations.

So, if the input is like nums = [8, 6, 6, 4, 3, 6, 6] k = 2, then the output will be 6, because we can change 4 and 3 to 6, to make this array [8, 6, 6, 6, 6, 6, 6], and the length of sublist with all 6s is 6.

To solve this, we will follow these steps −

• if nums is empty, then

  • return 0

• num_count := an empty map

• max_count := 0

• start := 0

• for each index end and value num in nums, do

  • num_count[num] := num_count[num] + 1

  • max_count := maximum of max_count and num_count[num]

  • if end - start + 1 > max_count + k, then

    • num_count[nums[start]] := num_count[nums[start]] - 1

    • start := start + 1

• return end - start + 1

Example

Let us see the following implementation to get better understanding

from collections import defaultdict
def solve(nums, k):
   if not nums:
      return 0

   num_count = defaultdict(int)
   max_count = 0
   start = 0

   for end, num in enumerate(nums):
      num_count[num] += 1
      max_count = max(max_count, num_count[num])
      if end - start + 1 > max_count + k:
         num_count[nums[start]] -= 1
         start += 1
   return end - start + 1

nums = [8, 6, 6, 4, 3, 6, 6]
k = 2
print(solve(nums, k))

Input

[8, 6, 6, 4, 3, 6, 6], 2

Output

6