Example 1:
Input: history = {1: ["M1", "M2", "M3", "M4", "M5"], 2: ["X", "Y", "M3", "M4", "M5"], 3: ["A", "B", "M3", "M4", "M5"]}, k = 3
Output: [[1, 2], [1, 3], [2, 3]]
Explanation:
Example 2:
Input: history = {1: ["A", "B", "C"], 2: ["X", "B", "C"], 3: ["A", "B", "C"]}, k = 3
Output: [[1, 3]]
Explanation:
Example 3:
Input: history = {1: ["A", "B"], 2: ["C", "D", "E"]}, k = 3
Output: []
Explanation:
Each customer has a list representing the movies they've watched in the order they were viewed. Two customers are considered "friends" if their recent viewing history is an exact match of the last k movies (same movies in the same order).
Given a map of customer IDs to their movie watch history and an integer k, return all pairs of customer IDs that are friends.
Notes:
k movies in their history, they cannot be friends with anyone.[1, 2] not [2, 1]).All three customers have the same last 3 movies ["M3", "M4", "M5"] in the same order, so all pairs are friends.
Only customers 1 and 3 have identical last 3 movies. Customer 2 has different first movie.
Customer 1 has only 2 movies, which is less than k=3, so no friends possible.
1 <= number of customers <= 10001 <= k <= 1000 <= history[i].length <= 1000