Destination City Python Solution with Tests

lcpy gen -n 1436   # by problem number
lcpy gen -s destination_city   # by problem name

Input: paths = [["London","New York"],["New York","Lima"],["Lima","Sao Paulo"]]
Output: "Sao Paulo"
Explanation: Starting at "London" city you will reach "Sao Paulo" city which is the destination city. Your trip consist of: "London" -> "New York" -> "Lima" -> "Sao Paulo".

Input: paths = [["B","C"],["D","B"],["C","A"]]
Output: "A"
Explanation: All possible trips are:
"D" -> "B" -> "C" -> "A".
"B" -> "C" -> "A".
"C" -> "A".
"A".
Clearly the destination city is "A".

Input: paths = [["A","Z"]]
Output: "Z"

class Solution:
    # Time: O(E) where E = len(paths)
    # Space: O(E)
    def dest_city(self, paths: list[list[str]]) -> str:
        outgoing = {src for src, _ in paths}
        for _, dst in paths:
            if dst not in outgoing:
                return dst
        return ""