On old cell phones, users typed on a numeric keypad and the phone would provide a list of words that matched these numbers. Each digit mapped to a set of 0 - 4 letters. Implement an algorithm to return a list of matching words, given a sequence of digits. You are provided a list of valid words. The mapping is shown in the diagram below:
Example 1:
Input: num = "8733", words = ["tree", "used"] Output: ["tree", "used"]
Example 2:
Input: num = "2", words = ["a", "b", "c", "d"] Output: ["a", "b", "c"]
Note:
num.length <= 1000words.length <= 500words[i].length == num.lengthThere are no number 0 and 1 in num.