46. Permutations #

Problem #

Given a collection of distinct integers, return all possible permutations.

Example:

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

Problem Summary #

Given a sequence with no duplicate numbers, return all possible permutations.

Solution Approach #

To find all permutations among the permutations and combinations of an array, simply use DFS.

Code #


package leetcode

func permute(nums []int) [][]int {
	if len(nums) == 0 {
		return [][]int{}
	}
	used, p, res := make([]bool, len(nums)), []int{}, [][]int{}
	generatePermutation(nums, 0, p, &res, &used)
	return res
}

func generatePermutation(nums []int, index int, p []int, res *[][]int, used *[]bool) {
	if index == len(nums) {
		temp := make([]int, len(p))
		copy(temp, p)
		*res = append(*res, temp)
		return
	}
	for i := 0; i < len(nums); i++ {
		if !(*used)[i] {
			(*used)[i] = true
			p = append(p, nums[i])
			generatePermutation(nums, index+1, p, res, used)
			p = p[:len(p)-1]
			(*used)[i] = false
		}
	}
	return
}