Recently I found some code that I can't understand, below is my code:
func subsetsWithDup(nums []int) [][]int {
if len(nums) == 0 {
return [][]int{[]int{}}
}
sort.Ints(nums)
result := [][]int{}
backtracking(nums, &result, []int{}, 0)
return result
}
func backtracking(nums []int, result *[][]int, tempList []int, start int) {
*result = append(*result, tempList)
for i := start; i < len(nums); i++ {
if i > start && nums[i] == nums[i-1] {
continue
}
tempList = append(tempList, nums[i])
backtracking(nums, result, tempList, i+1)
tempList = tempList[:len(tempList)-1:len(tempList)-1]
}
}
and another approach:
func subsetsWithDup(nums []int) [][]int {
sort.Ints(nums)
return subsets(nums, []int{}, [][]int{})
}
func subsets(nums []int, result []int, results [][]int) [][]int {
newR := make([]int, len(result))
copy(newR, result)
results = append(results, newR)
if len(nums) == 0 {return results}
for i := 0; i < len(nums); i++ {
if i > 0 && nums[i] == nums[i - 1] {continue}
result = append(result, nums[i])
results = subsets(nums[i + 1:], result, results)
result = result[:len(result) - 1]
}
return results
}
In the first approach, I use the following code :
tempList = tempList[:len(tempList)-1:len(tempList)-1]
it works, but if I change it to:
tempList = tempList[:len(tempList)-1]
it dose not work.In the second approach which use copy function also works. I want to know what happens behind the code, any help is appreciated, thanks.