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Given an unsorted integer array, find the smallest missing positive integer.

Example 1:

Input: [1,2,0]Output: 3

Example 2:

Input: [3,4,-1,1]Output: 2

Example 3:

Input: [7,8,9,11,12]Output: 1

Note:

Your algorithm should run in O(n) time and uses constant extra space.

---

 给定一个未排序的整数数组，找出其中没有出现的最小的正整数。

示例 1:

输入: [1,2,0]输出: 3

示例 2:

输入: [3,4,-1,1]输出: 2

示例 3:

输入: [7,8,9,11,12]输出: 1

说明:

你的算法的时间复杂度应为O(n)，并且只能使用常数级别的空间。

---

8ms

1 class Solution {2     func firstMissingPositive(_ nums: [Int]) -> Int {3         if nums.count == 0 {
   return 1}4         var nums = nums5         for i in 0..
     
      = 1 && nums[i] <= nums.count && nums[nums[i] - 1] != nums[i] {nums.swapAt(i, nums[i] - 1)}}6         for i in 0..
     

---

12ms

1 class Solution { 2     func firstMissingPositive(_ nums: [Int]) -> Int { 3         guard nums.count > 0 else { 4             return 1 5         } 6         var numsCopy = nums 7         for  i in 0..
     
       0 && numsCopy[i] < nums.count && numsCopy[numsCopy[i]-1] != numsCopy[i] { 9                  numsCopy.swapAt(i, numsCopy[i]-1)10             }11         }12         13         for i in 0..
     

---

12ms

1 class Solution { 2     func firstMissingPositive(_ nums: [Int]) -> Int { 3     var newNums = nums 4     for i in 0..
     
       i + 1 && newNums[i] <= nums.count && newNums[i] != newNums[newNums[i]-1] { 6             if newNums[i] <= nums.count && newNums[i] != newNums[newNums[i]-1] { 7                 let temp = newNums[i] 8                 newNums[i] = newNums[temp-1] 9                 newNums[temp-1] = temp10             }11         }12         if newNums[i] > 0 && i + 1 > newNums[i] {13             let temp = newNums[i]14             newNums[i] = newNums[temp-1]15             newNums[temp-1] = temp16         }17     }18     var i = 019     while i < nums.count {20         if i + 1 != newNums[i] {21             return i + 122         }23         i = i + 124     }25     return i + 126     }27 }
     

---

 16ms

1 class Solution { 2     func firstMissingPositive(_ nums: [Int]) -> Int { 3         var set = Set
     
      () 4          5         nums.forEach { set.insert($0) } 6          7         for i in 0..
     

---

16ms

1 class Solution { 2     func firstMissingPositive(_ nums: [Int]) -> Int { 3         if(nums.count == 0){ return 1 } 4         let maximum = nums.max()! 5         if(maximum > 0){ 6             for i in 1...maximum{ 7                 if(!nums.contains(i)){ 8                     return i 9                 }10             }11         }12         return maximum + 113     }14 }

---

20ms

1 class Solution { 2     func firstMissingPositive(_ nums: [Int]) -> Int { 3         var nums = nums 4         nums.append(-1) 5          6         if nums.count == 0 {
   return 1} 7         if nums.count == 1 {  return nums[0] == 1 ? 2 : 1 } 8          9         for i in 0..
     
      = 0 && nums[val] != val {12                 swap(&nums, i, val)13                 val = nums[i]14             }15             if val != i  {16                 nums[i] = -117             }18         }19         for i in 1..
     

---

32ms

1 class Solution {2     func firstMissingPositive(_ nums: [Int]) -> Int {3         for i in 1 ..< Int.max {4             if !nums.contains(i) { return i }5         }6         7         return Int.max8     }9 }