2024-02-20 Daily Challenge

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Today I have done leetcode's February LeetCoding Challenge with cpp.

February LeetCoding Challenge 20

Description

Missing Number

Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.

 

Example 1:

Input: nums = [3,0,1]
Output: 2
Explanation: n = 3 since there are 3 numbers, so all numbers are in the range [0,3]. 2 is the missing number in the range since it does not appear in nums.

Example 2:

Input: nums = [0,1]
Output: 2
Explanation: n = 2 since there are 2 numbers, so all numbers are in the range [0,2]. 2 is the missing number in the range since it does not appear in nums.

Example 3:

Input: nums = [9,6,4,2,3,5,7,0,1]
Output: 8
Explanation: n = 9 since there are 9 numbers, so all numbers are in the range [0,9]. 8 is the missing number in the range since it does not appear in nums.

 

Constraints:

  • n == nums.length
  • 1 <= n <= 104
  • 0 <= nums[i] <= n
  • All the numbers of nums are unique.

 

Follow up: Could you implement a solution using only O(1) extra space complexity and O(n) runtime complexity?

Solution

class Solution {
public:
  int missingNumber(vector<int>& nums) {
    int len = nums.size();
    int sum = (len + 1) * len / 2;
    for(auto i : nums) sum -= i;
    return sum;
  }
};

// Accepted
// 122/122 cases passed (11 ms)
// Your runtime beats 99.14 % of cpp submissions
// Your memory usage beats 93.84 % of cpp submissions (17.9 MB)
Algorithm