Search Insert Position

To solve this coding challenge, let's break down the problem and understand the requirements and constraints in detail before moving into the pseudocode solution.

Explanation

The task is to find the position at which a target value should be inserted into a sorted array of distinct integers if it is not already present in the array. If the target is present, we should simply return its index. We are required to implement this with a time complexity of \(O(\log n)\), indicating the use of a binary search approach.

Problem Breakdown:

  1. Input Description:
    • A sorted array
      nums
      of distinct integers.
    • An integer
      target
      .
  2. Output Description:
    • The index if the target is found.
    • The index where the target would be inserted to maintain sorted order if the target is not found.
  3. Constraints:
    • Array
      nums
      is sorted in ascending order.
    • Array
      nums
      contains distinct integers, so no duplicates are present.
    • Target and elements of the array are bounded by the range -10^4 to 10^4.
    • Array length ranges from 1 to 10^4.

    Approach:

    Given the requirement of \(O(\log n)\) time complexity, we will use a binary search algorithm. Binary search reduces the search range by half at each step, allowing us to efficiently find the target or the appropriate insertion position.
    High-Level Steps:
  4. Initialize two pointers,
    left
    and
    right
    , to the start (0) and end (length of the array - 1) of the array.
  5. While the
    left
    pointer does not exceed the
    right
    pointer:
    • Calculate the middle index,
      mid
      .
    • Compare the
      target
      with the middle element
      nums[mid]
      :
      • If
        nums[mid]
        equals
        target
        , return
        mid
        .
      • If
        target
        is greater than
        nums[mid]
        , move the
        left
        pointer to
        mid + 1
        .
      • If
        target
        is less than
        nums[mid]
        , move the
        right
        pointer to
        mid - 1
        .
  6. If the loop exits without finding the target, the
    left
    pointer will point to the insertion position where the target can be inserted in order.
  7. Detailed Steps in Pseudocode:

                                                
    function searchInsert(nums, target):
    # Initialize pointers for the binary search
    left = 0
    right = length of nums - 1
    
    # Binary search loop
    while left <= right:
    # Calculate the middle index
    mid = left + (right - left) // 2
    
    # Check if the middle element is the target
    if nums[mid] == target:
    return mid # Target found, return the index
    
    # If target is greater than middle element, search in the right half
    elif nums[mid] < target:
    left = mid + 1
    
    # If target is less than middle element, search in the left half
    else:
    right = mid - 1
    
    # If we exit the loop, left is the insertion point
    return left
    
                                            

    Explanation of Pseudocode:

  8. Initialization:
    •                                             
      left = 0
      right = length of nums - 1
      
                                              
    • left
      and
      right
      variables are initialized to point to the first and last index of the array, respectively.
  9. Binary Search Loop:
    •                                             
      while left <= right:
      mid = left + (right - left) // 2
      
                                              
    • This loop continues as long as
      left
      is less than or equal to
      right
      .
    • mid
      is recalculated in each iteration to find the middle index of the current search range.
  10. Comparison and Adjustment of Search Range:
    •                                             
      if nums[mid] == target:
      return mid
      
      elif nums[mid] < target:
      left = mid + 1
      
      else:
      right = mid - 1
      
                                              
    • If the middle element equals the target, return
      mid
      .
    • If the target is greater than the middle element, narrow the search to the right half by setting
      left
      to
      mid + 1
      .
    • If the target is less than the middle element, narrow the search to the left half by setting
      right
      to
      mid - 1
      .
  11. Insertion Position:
    •                                             
      return left
      
                                              
    • If the loop exits without finding the target,
      left
      will be the insertion point.
By following these steps, we ensure an \(O(\log n)\) time complexity while finding the target or determining its correct insertion position in the sorted array.