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Problem solution · Python

CCC 2018 S1 - Voronoi Villages

CCC 2018 S1 - Voronoi Villages: a Python solution using sliding window or two pointers. Learn the idea, check the complexity, and read the full code, with credit to CCCSolutions.

Technique
Sliding window or two pointers
Source
CCCSolutions
Length
22 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

Sliding window or two pointers

For CCC 2018 S1 - Voronoi Villages, the implementation maintains a moving interval and updates only the information that enters or leaves the window.

  1. Choose the invariant that makes a window valid or useful.
  2. Advance the right boundary and add the new element.
  3. Move the left boundary only as needed while maintaining the invariant and updating the answer.

Code notes

  • 22 lines of Python from the credited upstream file ccc18s1.py.
  • The implementation visibly relies on sequence storage.
  • No explicit loop blocks detected.

Complexity

Confirm that neither pointer moves backwards; if so, the scan is usually linear apart from the window’s data-structure operations.

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

Source

Code and credit

This code comes from CCCSolutions by CCCSolutions contributors · Milliken Mills High School and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeCCC 2018 S1 - Voronoi Villages · PythonPython
Use this to learn the idea, then write your own version.
# By Oscar Zhou, Abbey Park High School# This solution still requires commented explanations. Please feel free to add them! # https://dmoj.ca/problem/ccc18s1 import sysinput = sys.stdin.readline n = int(input()) v = [] for i in range(n):    v.append(int(input()))v.sort() ans = float("inf")for i in range(1, n-1):    left = (v[i] + v[i-1])/2    right = (v[i] + v[i+1])/2    ans = min(ans, right-left)print(ans)

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