題目網址: https://www.puzzleup.com/2021/
https://www.puzzleup.com/2021/puzzle/?5
答題時限: ９月30日７ＰＭ－比賽結束（約11月９日）
加分時限: ９月30日７ＰＭ－10月５日６：５９ＰＭ
答對可得基本分１００分。答案可上傳５次，每改１次答案從基本分扣２０分。　
比賽期間內可隨時上傳答案，加分時限內答對第ｎ天加（６－ｎ）分　 　　 　　
另依題目的難易有額外加分（如有８０％的人這題答錯，答對者加８０分）　　
◆GRID PAINTING
You have 3 different colors to paint the squares of a 3x3 grid.
-The total number of squares to be painted is 5.
-Each painted square must be adjacent (horizontally or vertically) to another
painted square.
-Adjacent squares (horizontally or vertically) should be painted in different
colors.
How many different ways can this task be done?
Notes:
-All three colors must be used.
-Disconnected groups of connected squares are allowed.
將三個顏色塗在一個 3x3 格子中。
- 恰好塗五個格子。
- 任何塗色格子需要水平或垂直相鄰另一個塗色格子。
- 而如此相鄰的兩個塗色格子需要不同顏色。
試問這樣的塗色法有多少種？
註:
- 三種顏色均要使用。
- 允許有兩群連續的格子彼此不相鄰。
If the problem was asked for 2x2 grid and 2 different colors, and the number
of squares to paint was 3, the answer would be 8.
若此問題改問 2x2 格子，兩種顏色，塗三格，則答案為 8:
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