Problem Description
Given an array of integers colors, representing a circle of tiles where 0 means red and 1 means blue, return the number of contiguous groups of 3 tiles that have alternating colors. The tiles are considered to be in a circle, so the first and last tiles are adjacent.
Key Insights
- An alternating group consists of three contiguous tiles where the middle tile is of a different color than its neighbors.
- Since the tiles are arranged in a circle, the last tile is adjacent to the first tile.
- We need to check each triplet of tiles, including the wrap-around case involving the last and first tiles.
Space and Time Complexity
Time Complexity: O(n)
Space Complexity: O(1)
Solution
To solve the problem, we can use a simple loop to iterate through the array of colors and count the number of valid alternating groups. For each index i, we will check the triplet starting at i, which includes the current tile, the next tile, and the tile after that. We will also need to handle the circular condition by wrapping around the indices when they exceed the array bounds.