46. Permutations

題目描述

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

範例

Example 1:

Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Example 2:

Input: nums = [0,1]
Output: [[0,1],[1,0]]

Example 3:

Input: nums = [1]
Output: [[1]]

Constraints:

• 1 <= nums.length <= 6
• -10 <= nums[i] <= 10
• All the integers of nums are unique.

解答

Python

內建作弊 by itertools

class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        return list(permutations(nums))

class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        res = []

        def backtrack(arr):
            if len(arr) == len(nums):
                res.append(arr.copy())
                return

            for num in nums:
                if num not in arr:
                    arr.append(num)
                    backtrack(arr)
                    arr.pop()

        backtrack([])
        return res

Ron ChenWed, Aug 2, 2023

C++

class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> ans;
        backtrack(nums, 0, ans);
        return ans;
    }

    void backtrack(vector<int>& nums, int first, vector<vector<int>>& ans) {
        if (first >= nums.size()) {
            ans.push_back(nums);
        }
        for (int i = first; i < nums.size(); i ++) {
            swap(nums[first], nums[i]);
            backtrack(nums, first + 1, ans);
            swap(nums[first], nums[i]);
        }
    }
};

Jerry Wu2 August, 2023

Reference

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