# [Leetcode] Training day-001

1640. Check Array Formation Through Concatenation

You are given an array of distinct integers arr and an array of integer arrays pieces, where the integers in pieces are distinct. Your goal is to form arr by concatenating the arrays in pieces in any order. However, you are not allowed to reorder the integers in each array pieces[i].

Return true if it is possible to form the array arr from pieces. Otherwise, return false.

**Constraints:**1 <= pieces.length <= arr.length <= 100

sum(pieces[i].length) == arr.length

1 <= pieces[i].length <= arr.length

1 <= arr[i], pieces[i][j] <= 100

The integers in arr are distinct.

The integers in pieces are distinct (i.e., If we flatten pieces in a 1D array, all the integers in this array are distinct).

參考解答：hashmap

1641. Count Sorted Vowel Strings

Given an integer n, return the number of strings of length n that consist only of vowels (a, e, i, o, u) and are lexicographically sorted.

A string s is lexicographically sorted if for all valid i, s[i] is the same as or comes before s[i+1] in the alphabet.

給訂的數字n，依序排列出所有的母音n個拼音的總組合數，且必須維持母音原有的字母順序，不可順序錯置。？？？

**Constraints:**

1 <= n <= 50

參考答案：Link