Difficulty – Hard

Hard brain teasers and puzzles

Cryptography and Codes, Difficulty - Hard, Interview Brain Teasers, Word Puzzles

Secret Translation

The CIA intercepted some messages from a criminal organization, some in English and some in an unknown foreign language or code. As a CIA analyst and translator, you have figured out the following sentences and their English translations, but you do not yet know which sentence matches which translation:

Casara ashter osar
Intara amar
Intara orter osar
Alatara inter osar
Ortara amar
Alatara orter osar

I see a spy
I run
You see me
You see a spy
A suspicious man sees an enemy
You run

You have the opportunity to send a message in order to provoke a reaction from the criminal organization. Can you figure out and match up the translations above, and then send a message saying “a suspicious man runs” in this foreign language?

Chess, Difficulty - Hard

Take Back a Move Chess Puzzle

This creative Leonid Kubbel chess puzzle has white take back a move and then checkmate!

White just made a move, but then realized there was a mate in 1 on the last move and missed it. What was white’s last move, and what was the mate in 1?

Difficulty - Hard, Patterns, Sequences, and Sets, Word Puzzles

Cryptic Pattern Puzzle

Replace the ?’s in each of these to complete the puzzle:

Part 1

“Asia” is H
“Cuffs” is S
“Ender” is I
“Redness” is F
“Fuchsia” is ?

Part 2

“Using” is E
“Desist” is I
“Visits” is E
“Design” is ?

Part 3

“Gross” is W or R
“Assign” is S
“Amassing” is E
“Design” is S
“Amassing” is S
“Arrows” is ? or ?

Part 4

“Pro-tem” and “row” are H
“Ties” is K
“Cohesion” is A
“Casino” is E
“Hocks” is either a word, name, ? or ?

Part 5

“Edna” is I
“Slang” is X
“Siege” is E
“Basin” is X
“Sin” is X
“Sin” is A
“Besiege” is X
“Signals” is ? and ?

Source: Matt Malone on Puzzling StackExchange (spoiler warning: contains the solution)

Difficulty - Hard, Interview Brain Teasers, Logic Puzzles

Island of Blue Eyes

There is an island known for its people with blue eyes, yet there is at least one green-eyed person on the island. No one knows the color of their own eyes, as there are no reflective surfaces on the island and discussion of eye color is forbidden, but they can see everyone else’s eye color. If any islander were to come to know that they do not have blue eyes, they would leave the island in shame before the next sunrise.

One day, an outsider visits the island and remarked how there was at least one islander with green eyes. Within the day, every islander had heard and understood this new information.

Assuming departures from the island are noticed by everyone by the next day, and assuming each islander is highly logical and is able to keep track of all other islanders’ eye colors and actions – what happens to the islanders and does it depend on the number of green-eyed islanders?

This is a classic logic puzzle, also known under a different story (but same core logic) as Josephine’s Problem.