2021-11-18 Daily-Challenge

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In: DailyChallenge
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Today I have done leetcode's November LeetCoding Challenge with cpp.

November LeetCoding Challenge 18

Description

Find All Numbers Disappeared in an Array

Given an array nums of n integers where nums[i] is in the range [1, n], return an array of all the integers in the range [1, n] that do not appear in nums.

Example 1:

Input: nums = [4,3,2,7,8,2,3,1]
Output: [5,6]

Example 2:

Input: nums = [1,1]
Output: [2]

Constraints:

  • n == nums.length
  • 1 <= n <= 10^5
  • 1 <= nums[i] <= n

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

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  vector<int> findDisappearedNumbers(vector<int>& nums) {
    for(auto i : nums) {
      i = i < 0 ? -i : i;
      nums[i - 1] = nums[i - 1] < 0 ? nums[i - 1] : -nums[i - 1];    
    }
    vector<int> answer;
    for(int i = 0; i < nums.size(); ++i) {
      if(nums[i] > 0) {
        answer.push_back(i + 1);
      }
    }
    return answer;
  }
};

// Accepted
// 33/33 cases passed (28 ms)
// Your runtime beats 99.89 % of cpp submissions
// Your memory usage beats 54.3 % of cpp submissions (33.8 MB)
Algorithm