105 - 448找到数组中消失的数字

题目

给定一个范围在 1 ≤ a[i] ≤ n ( n = 数组大小 ) 的 整型数组，数组中的元素一些出现了两次，另一些只出现一次。

找到所有在 [1, n] 范围之间没有出现在数组中的数字。

您能在不使用额外空间且时间复杂度为O(n)的情况下完成这个任务吗? 你可以假定返回的数组不算在额外空间内。

示例:

输入: [4,3,2,7,8,2,3,1]

输出: [5,6]

解答

python里面有一个，判断是否在数组里面的方法。

或者用set先去重，然后排序，然后一个个比对没有的。

加数组长度

作者：haydenmiao 链接：https://leetcode-cn.com/problems/find-all-numbers-disappeared-in-an-array/solution/cyuan-shu-zu-cao-zuo-by-haydenmiao/

因为可能的最大值是数组长度，因此每个值都加一下数组长度，以此来标记，就能区分哪些有哪些没有。

每次加的时候都用%来取消掉加的影响。

func findDisappearedNumbers(nums []int) []int {
    if len(nums) == 0 {
        return nums
    }
    for i := 0; i < len(nums); i++ {
        index := (nums[i] - 1) % len(nums)
        nums[index] += len(nums)
    }
    res := make([]int, 0, len(nums))
    for i := 0; i < len(nums); i++ {
        if nums[i] <= len(nums) {
            res = append(res, i+1)
        }
    }
    return res
}

Runtime: 384 ms, faster than 57.19% of Go online submissions for Find All Numbers Disappeared in an Array.

Memory Usage: 8.2 MB, less than 75.00% of Go online submissions for Find All Numbers Disappeared in an Array.

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var findDisappearedNumbers = function (nums) {
  if (nums.length === 0) {
    return [];
  }
  for (let i = 0; i < nums.length; i++) {
    let index = (nums[i] - 1) % nums.length;
    nums[index] += nums.length
  }
  let res = []
  for (let i = 0; i < nums.length; i++) {
    if (nums[i] <= nums.length) {
      res.push(i + 1)
    }
  }
  return res
};

Runtime: 100 ms, faster than 81.47% of JavaScript online submissions for Find All Numbers Disappeared in an Array.

Memory Usage: 43.7 MB, less than 75.00% of JavaScript online submissions for Find All Numbers Disappeared in an Array.

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        if len(nums) == 0:
            return []
        for i in range(len(nums)):
            index = (nums[i] - 1) % len(nums)
            nums[index] += len(nums)
        res = []
        for i in range(len(nums)):
            if nums[i] <= len(nums):
                res.append(i + 1)
        return res

Runtime: 460 ms, faster than 14.54% of Python3 online submissions for Find All Numbers Disappeared in an Array.

Memory Usage: 21.6 MB, less than 14.29% of Python3 online submissions for Find All Numbers Disappeared in an Array.

变成负数

作者：gehui1007 链接：https://leetcode-cn.com/problems/find-all-numbers-disappeared-in-an-array/solution/ti-jie-bu-shi-yong-e-wai-kong-jian-by-gehui1007/

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        for num in nums:
            index = abs(num) - 1
            nums[index] = -abs(nums[index])
        return [i + 1 for i, num in enumerate(nums) if num > 0]

Runtime: 424 ms, faster than 50.58% of Python3 online submissions for Find All Numbers Disappeared in an Array.

Memory Usage: 21.6 MB, less than 14.29% of Python3 online submissions for Find All Numbers Disappeared in an Array.

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var findDisappearedNumbers = function (nums) {
  for (const num of nums) {
    let index = Math.abs(num) - 1
    nums[index] = -Math.abs(nums[index])
  }
  let res = []
  for (let i = 0; i < nums.length; i++) {
    if (nums[i] > 0) {
      res.push(i + 1)
    }
  }
  return res
};

Runtime: 96 ms, faster than 88.72% of JavaScript online submissions for Find All Numbers Disappeared in an Array.

Memory Usage: 44 MB, less than 25.00% of JavaScript online submissions for Find All Numbers Disappeared in an Array.

func abs(a int) int {
    if a < 0 {
        return -a
    }
    return a
}
func findDisappearedNumbers(nums []int) []int {
    for _, value := range nums {
        index := abs(value) - 1
        nums[index] = -abs(nums[index])
    }
    res := make([]int, 0, len(nums))
    for i := 0; i < len(nums); i++ {
        if nums[i] > 0 {
            res = append(res, i+1)
        }
    }
    return res
}

Runtime: 376 ms, faster than 81.40% of Go online submissions for Find All Numbers Disappeared in an Array.

Memory Usage: 9 MB, less than 25.00% of Go online submissions for Find All Numbers Disappeared in an Array.