Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.

Find all the elements of [1, n] inclusive that do not appear in this array.

Could you do it without extra space and in O(n) runtime? You may assume the returned list does not count as extra space.

Example:

Input:
[4,3,2,7,8,2,3,1]

Output:
[5,6]

給定一個範圍在  1 ≤ a[i] ≤ n ( n = 陣列大小 ) 的 整型陣列，陣列中的元素一些出現了兩次，另一些只出現一次。

找到所有在 [1, n] 範圍之間沒有出現在陣列中的數字。

您能在不使用額外空間且時間複雜度為O(n)的情況下完成這個任務嗎? 你可以假定返回的陣列不算在額外空間內。

示例:

輸入:
[4,3,2,7,8,2,3,1]

輸出:
[5,6]

80ms

 1 class
 
 Solution {
 2     func findDisappearedNumbers(_ nums: [Int]) -> [Int] {
 3         
 4         var input = nums
 5         var result: [Int] = []
 6         
 7         for i in 0..<input.count{
 8             var check = -1
 9             
10             if input[i] > 0{
11                 check = input[i] - 1
 

12             }else{
13                 check = (input[i] * (-1)) - 1
14             }
15             
16             if input[check] > 0{
17                 input[check] = (input[check] * (-1))
18             }
19             
20         }
21         
22         for i in 0..<input.count{
23             if input[i] > 0 {
24                 result.append(i+1)
25             }
26         }
27         
28         return result
29     }
30 }

88ms

 1 class Solution {
 2     func findDisappearedNumbers(_ nums: [Int]) -> [Int] {
 3         var list = nums
 4         var results = [Int]()
 5 
 6         for i in 0 ..< list.count {
 7             let idx = abs(list[i]) - 1
 8             list[idx] = (list[idx] > 0) ? -list[idx] : list[idx]
 9         }
10 
11         for i in 0 ..< list.count {
12             if (0 < list[i]) {
13                 results.append(i + 1)
14             }
15         }
16 
17         return results
18     }
19 }

104ms

 1 class Solution {
 2     func findDisappearedNumbers(_ nums: [Int]) -> [Int] {
 3         let test = 0
 4         if test == 0 {        
 5             var result = [Int]()
 6             var explored = [Bool](repeating: false, count: nums.count+1)
 7 
 8             for num in nums {
 9                 explored[num] = true
10             }
11 
12             var i = 1
13             while i < explored.count {
14                 if explored[i] == false {
15                     result.append(i)
16                 }
17 
18                 i += 1
19             }
20 
21             return result
22         }
23         
24         if test == 1 {        
25             var result = [Int]()
26             var nums = nums
27 
28             var i = 0
29             while i < nums.count {
30                 while nums[i] != nums[nums[i]-1] {
31                     nums.swapAt(i, nums[i]-1)
32                 }
33 
34 
35                 i += 1
36             }
37 
38             var j = 0
39             while j < nums.count {
40                 if j+1 != nums[j] {
41                     result.append(j+1)
42                 }
43 
44                 j += 1
45             }
46 
47             return result
48         }
49     }
50 }

112ms

 1 class Solution {
 2     func findDisappearedNumbers(_ nums: [Int]) -> [Int] {
 3         var nums = nums
 4         for idx in 0..<nums.count {
 5             let nextIdx = abs(nums[idx]) - 1
 6             nums[nextIdx] = nums[nextIdx] < 0 ? nums[nextIdx] : -nums[nextIdx]
 7         }
 8         var ans = [Int]()
 9         for idx in 0..<nums.count {
10             if nums[idx] > 0 {
11                 ans.append(idx + 1)
12             }
13         }
14         return ans
15     }
16 }

124ms

 1 class Solution {
 2     func findDisappearedNumbers(_ nums: [Int]) -> [Int] {
 3         var nums = nums
 4 
 5         for i in 0..<nums.count {
 6             if nums[abs(nums[i]) - 1] > 0 {
 7                 nums[abs(nums[i]) - 1] *= -1
 8             }
 9         }
10 
11         var res = [Int]()
12 
13         for i in 0..<nums.count {
14             if nums[i] > 0 {
15                 res.append(i + 1)
16             } else {
17                 nums[i] *= -1
18             }
19         }
20 
21         return res
22     }
23 }