Words are sorted according to an unknown order of lowercase letters. Return any ordering of exactly the letters that occur, consistent with this sorted list. Return an empty string for a contradictory order or a longer word before its own prefix.
Example 1
Character precedence from the first differing letters of adjacent words: za, zb, ca, cb. A longer word before its own prefix is invalid.
Input
words = ["za","zb","ca","cb"]
Output
"abzc"
Explanation
Comparisons require a before b and z before c; abzc contains all letters and respects both.
Example 2
Character precedence from the first differing letters of adjacent words: abc, ab. A longer word before its own prefix is invalid.
Input
words = ["abc","ab"]
Output
""
Explanation
A longer word cannot precede its own exact prefix under any letter ordering.
Example 3
Character precedence from the first differing letters of adjacent words: z, x, z. A longer word before its own prefix is invalid.
Input
words = ["z","x","z"]
Output
""
Explanation
The comparisons demand both z before x and x before z, a contradiction.
Example 4
Character precedence from the first differing letters of adjacent words: a. A longer word before its own prefix is invalid.
Input
words = ["a"]
Output
"a"
Explanation
Only a occurs, so the one-letter ordering a satisfies all comparisons.
Constraints
1 <= number of words <= 100
Each word has 1..100 lowercase English letters
Function contractalienOrderArguments: json
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