46. Permutations ⭐

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

解題

講得不錯的解說​
Runtime: 0 ms, faster than 100%
Memory Usage: 2.5 MB, less than 87.18%
func permute(nums []int) [][]int {
ans := make([][]int, 0)
perm := make([]int, len(nums))
visited := make([]bool, len(nums)) // 一個狀態變量儲存整個狀態樹
​
var backtracking func(int)
backtracking = func(index int) {
if index == len(nums) {
ans = append(ans, append([]int{}, perm...))
return
}
​
for i:=0; i<len(nums); i++ {
if !visited[i] {
visited[i] = true
perm[index] = nums[i]
backtracking(index+1)
visited[i] = false // 撤銷選擇
}
}
}
​
backtracking(0)
​
return ans
}