Leetcode 2239: Find Closest Number to Zero

Input: An integer array nums of size n where each element can be negative, positive, or zero.

Example: Input: nums = [-7, 2, 3, -3, 5]

Constraints:

• 1 <= n <= 1000

• -105 <= nums[i] <= 105

Output: Return the integer from the array that is closest to 0. If multiple numbers are equally close, return the largest value.

Example: Output: -3

Constraints:

• The output must be a single integer from the input array.

Goal: Find the number closest to 0 based on its absolute value. If two numbers have the same absolute value, select the larger one.

Steps:

• 1. Iterate through all elements in the array.

• 2. Compare the absolute values of each number to determine the closest to 0.

• 3. If two numbers have the same absolute value, select the one with the larger value.

• 4. Return the resulting number.

Goal: The input array will always have at least one element, and each number is within the specified range.

Steps:

• 1 <= n <= 1000

• -105 <= nums[i] <= 105

Assumptions:

• The input array will never be empty.

• All values in the array are integers.

• Input: Input: nums = [-7, 2, 3, -3, 5]

• Explanation: The absolute values are [7, 2, 3, 3, 5]. Both 3 and -3 are equally close to 0, but 3 is larger. So, the output is 3.

• Input: Input: nums = [4, -4, 1]

• Explanation: The absolute values are [4, 4, 1]. Both 4 and -4 are equally close to 0, but 4 is larger. So, the output is 4.

Approach: Use a simple comparison of absolute values with a condition to handle ties for equally close numbers.

Observations:

• The absolute value comparison is key to determining closeness to 0.

• Handling ties by choosing the larger number ensures uniqueness in the output.

• Iterating through the array while maintaining a variable for the current closest value is efficient for solving the problem.

Steps:

• 1. Initialize a variable to hold the closest number, starting with the first element in the array.

• 2. Loop through the array to compare the absolute value of each number to the current closest value.

• 3. If a number has a smaller absolute value, update the closest number.

• 4. If a number has the same absolute value but is larger, update the closest number.

• 5. Return the final closest number.

Empty Inputs:

• Not applicable, as input size is guaranteed to be at least 1.

Large Inputs:

• An array with 1000 elements containing a mix of large positive and negative numbers, e.g., nums = [-105, 105, -50, 50].

Special Values:

• Array contains zeros, e.g., nums = [0, -1, 1].

• Array contains duplicate values, e.g., nums = [-5, 5, -5].

Constraints:

• All integers in the array should be within the range -105 to 105.

  int findClosestNumber(vector<int>& nums) {
return *min_element(begin(nums), end(nums), [](int a, int b) {
    return abs(a) < abs(b) || (abs(a) == abs(b) && a > b);
});
  }

1 : Function Definition

  int findClosestNumber(vector<int>& nums) {

This is the definition of the 'findClosestNumber' function that takes a vector of integers and returns an integer, which is the closest to zero.

2 : Finding Minimum Element

return *min_element(begin(nums), end(nums), [](int a, int b) {

This line uses the 'min_element' algorithm to find the closest number to zero in the array, using a lambda function to compare absolute values.

3 : Comparison Logic

    return abs(a) < abs(b) || (abs(a) == abs(b) && a > b);

The lambda function compares two integers by their absolute value. If the absolute values are equal, it returns the larger number.

Best Case: O(n)

Average Case: O(n)

Worst Case: O(n)

Description: The time complexity is linear since the array is traversed once.

Best Case: O(1)

Worst Case: O(1)

Description: No additional space is used beyond a few variables for tracking the result.

Leetcode 2239: Find Closest Number to Zero

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