LeetCode 1460. Make Two Arrays Equal by Reversing Subarrays

原题链接在这里：https://leetcode.com/problems/make-two-arrays-equal-by-reversing-subarrays/description/

题目：

You are given two integer arrays of equal length target and arr. In one step, you can select any non-empty subarray of arr and reverse it. You are allowed to make any number of steps.

Return true if you can make arr equal to target or false otherwise.

Example 1:

Input: target = [1,2,3,4], arr = [2,4,1,3]
Output: true
Explanation: You can follow the next steps to convert arr to target:
1- Reverse subarray [2,4,1], arr becomes [1,4,2,3]
2- Reverse subarray [4,2], arr becomes [1,2,4,3]
3- Reverse subarray [4,3], arr becomes [1,2,3,4]
There are multiple ways to convert arr to target, this is not the only way to do so.

Example 2:

Input: target = [7], arr = [7]
Output: true
Explanation: arr is equal to target without any reverses.

Example 3:

Input: target = [3,7,9], arr = [3,7,11]
Output: false
Explanation: arr does not have value 9 and it can never be converted to target.

Constraints:

• target.length == arr.length
• 1 <= target.length <= 1000
• 1 <= target[i] <= 1000
• 1 <= arr[i] <= 1000

题解：

The idea behind is to check if they are anagram.

Time Complexity: O(n). n = target.length.

Space: O(n).

AC Java:

class Solution {
    public boolean canBeEqual(int[] target, int[] arr) {
        if(target.length != arr.length){
            return false;
        }
        
        HashMap<Integer, Integer> hm = new HashMap<>();
        for(int num : target){
            hm.put(num, hm.getOrDefault(num, 0) + 1);
        }
        
        for(int num : arr){
            if(!hm.containsKey(num) || hm.get(num) <= 0){
                return false;
            }
            
            hm.put(num, hm.get(num) - 1);
        }
        
        return true;
    }
}