置换Leetcode

def permute(nums):
    def backtrack(first=0):
        if first == n:
            output.append(nums[:])
        for i in range(first, n):
            nums[first], nums[i] = nums[i], nums[first]
            backtrack(first + 1)
            nums[first], nums[i] = nums[i], nums[first]

    n = len(nums)
    output = []
    backtrack()
    return output

def checkPermutation(arr1, arr2):
    if len(arr1) != len(arr2):
        return False
    return sorted(arr1) == sorted(arr2)

def checkPermutation(arr1, arr2):
    if len(arr1) != len(arr2):
        return False
    count = {}
    for num in arr1:
        count[num] = count.get(num, 0) + 1
    for num in arr2:
        if num not in count or count[num] == 0:
            return False
        count[num] -= 1
    return True