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Problem solution · Python

Find the Integer Added to Array II

Find the Integer Added to Array II: a Python solution using sorting and greedy selection. Learn the idea, check the complexity, and read the full code, with credit to walkccc LeetCode Solutions.

Technique
Sorting and greedy selection
Source
walkccc LeetCode Solutions
Length
36 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Sorting and greedy selection

For Find the Integer Added to Array II, the implementation first exposes a useful order, then scans that order while making locally justified choices.

  1. Choose the key that reveals the greedy or grouping structure.
  2. Sort the relevant records by that key.
  3. Scan in order, maintaining the invariant that makes each local choice safe.

Code notes

  • 36 lines of Python from the credited upstream file 3132.py.
  • The implementation visibly relies on sequence storage.
  • No explicit loop blocks detected.

Complexity

Sorting is typically the dominant term unless the subsequent scan uses a more expensive nested operation.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from walkccc LeetCode Solutions by P.-Y. Chen (walkccc) and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeFind the Integer Added to Array II · PythonPython
Use this to learn the idea, then write your own version.
class Solution:  def minimumAddedInteger(self, nums1: list[int], nums2: list[int]) -> int:    # After removing two elements from nums1, either nums1[0], nums1[1], or    # nums1[2] will persist. Therefore, the difference between nums1 (with two    # elements removed) and nums2 is represented by nums2[0] - nums1[i], where    # 0 <= i <= 2.    ans = math.inf     nums1.sort()    nums2.sort()     for i in range(3):      inc = nums2[0] - nums1[i]      if self._isValidDiff(nums1, nums2, inc):        ans = min(ans, inc)     return ans   def _isValidDiff(self, nums1: list[int], nums2: list[int], inc: int) -> bool:    """    Returns True if it's possible to increase nums1 (with two elements removed)    by `inc` to nums2.    """    removed = 0    i = 0  # nums2's index     for num in nums1:      if num + inc == nums2[i]:        i += 1        if i == len(nums2):          break      else:        removed += 1     return removed <= 2

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