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1640. Check Array Formation Through Concatenation

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Description

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.

 

Example 1:

Input: arr = [85], pieces = [[85]]
Output: true

Example 2:

Input: arr = [15,88], pieces = [[88],[15]]
Output: true
Explanation: Concatenate [15] then [88]

Example 3:

Input: arr = [49,18,16], pieces = [[16,18,49]]
Output: false
Explanation: Even though the numbers match, we cannot reorder pieces[0].

Example 4:

Input: arr = [91,4,64,78], pieces = [[78],[4,64],[91]]
Output: true
Explanation: Concatenate [91] then [4,64] then [78]

Example 5:

Input: arr = [1,3,5,7], pieces = [[2,4,6,8]]
Output: 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).

Solutions

Python3

class Solution:
    def canFormArray(self, arr: List[int], pieces: List[List[int]]) -> bool:
        mapper = {piece[0]: piece for piece in pieces}
        i, n = 0, len(arr)
        while i < n:
            if arr[i] not in mapper:
                return False
            vals = mapper[arr[i]]
            for val in vals:
                if arr[i] != val:
                    return False
                i += 1
        return True

Java

class Solution {
    public boolean canFormArray(int[] arr, int[][] pieces) {
        Map<Integer, int[]> map = new HashMap<>();
        for (int[] piece : pieces) {
            map.put(piece[0], piece);
        }
        for (int i = 0; i < arr.length;) {
            int[] vals = map.get(arr[i]);
            if (vals == null) {
                return false;
            }
            for (int val : vals) {
                if (arr[i] != val) {
                    return false;
                }
                ++i;
            }
        }
        return true;
    }
}

JavaScript

/**
 * @param {number[]} arr
 * @param {number[][]} pieces
 * @return {boolean}
 */
var canFormArray = function (arr, pieces) {
    let mapper = new Map();
    for (let i = 0; i < pieces.length; i++) {
        mapper.set(pieces[i][0], pieces[i]);
    }
    let i = 0,
        n = arr.length;
    while (i < n) {
        let cur = arr[i];
        let nums = mapper.get(cur);
        if (nums == undefined) return false;
        for (let num of nums) {
            if (arr[i] != num) return false;
            i++;
        }
    }
    return true;
};

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