Alien Dictionary
Given a sorted alien dictionary, find character order Compare adjacent words to determine character precedence Example: ["wrt", "wrf"] -> 't' comes before 'f' ["er", "ett"] -> 'r' comes before 't'
Given words sorted in an alien language, figure out the alphabet order. It's a graph problem in disguise: each pair of adjacent words gives you ordering constraints, and you need to find an order that satisfies all of them. The gotcha is detecting when no valid order exists—cycles in your constraint graph mean the input is invalid.
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