National Zoo

It’s always a challenge to find where the animals are.

Snake Pit

Place snakes and identify their heads such that:

• No snake orthogonally touches another snake of the same length
• Snakes are one-cell-wide paths that do not touch themselves, even diagonally
• The snakes have a head and a tail (there are no one-cell snakes)
• No snake head can share an edge with another snake’s head or tail
• Numbers present indicate the length of the snake in that cell
• All cells are occupied by exactly one snake

Example and Solution

(emoji represent the heads of each snake)

Penguin Floes

Identify ice floes such that:

• No floes share an edge
• Each floe has exactly one number, and the number of cells in the floe is equal to that number
• All water cells are edge-connected
• No 2x2 square of water cells is present

At the same time, place penguins such that:

• There is exactly one penguin on each ice floe
• Each penguin is on the cell of its floe whose 8 surrounding cells contain the longest continuous stretch of water

Example and Solution

Fish Tanks

• Each region represents an aquarium that can be filled with water
• Within an aquarium, the water reaches a certain number of cells up from its bottommost cell(s)
• Shade cells to represent a water-filled cell, blank to represent an empty cell
• Numbers on the outside represent the number of shaded/water-filled cells

At the same time, place fish in the tanks such that:

• There are two fish in each aquarium, row, and column
• All fish are within the water

Example and Solution

Bat cave

• Shade some cells to leave behind an unshaded cave
• Numbers cannot be shaded
• The cave is edge-connected
• All shaded regions are edge-connected to the boundary
• The number indicates the cells visible from there (horizontally and vertically, including self)

At the same time, place bats in the cave such that:

• Each cell in the cave can be seen by at least one bat
• No bat can see another bat
• No bat occupies a number cell

Example and Solution

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