Python: Find the starting and ending position of a given value in a given array of integers, sorted in ascending order

Last update on April 17 2025 13:01:16 (UTC/GMT +8 hours)

Find Value Range in Array

Write a Python program to find the starting and ending position of a given value in an array of integers, sorted in ascending order.
If the target is not found in the array, return [-1, 0].
Input: [5, 7, 7, 8, 8, 8] target value = 8
Output: [3, 5]
Input: [1, 3, 6, 9, 13, 14] target value = 4
Output: [-1, 0]

Sample Solution:

Python Code:

# Define a function to find the range of indices for a target value in a sorted list
def search_Range(array_nums, target_val):
    # Initialize an empty list to store the result
    result_arra = []
    
    # Initialize variables for start and end positions
    start_pos = -1
    end_pos = 0
    
    # Iterate through the list
    for i in range(len(array_nums)):
        # Check if the current element is equal to the target value and start_pos is -1
        if target_val == array_nums[i] and start_pos == -1:
            # Set start_pos to the current index
            start_pos = i
            # Set end_pos to the current index
            end_pos = i
        # Check if the current element is equal to the target value and start_pos is not -1
        elif target_val == array_nums[i] and start_pos != -1:
            # Update end_pos to the current index
            end_pos = i
    
    # Append start_pos and end_pos to the result list
    result_arra.append(start_pos)
    result_arra.append(end_pos)
    
    # Return the result list
    return result_arra

# Test the function with different lists and target values, and print the results
print(search_Range([5, 7, 7, 8, 8, 8], 8))        
print(search_Range([1, 3, 6, 9, 13, 14], 4))      
print(search_Range([5, 7, 7, 8, 10], 8))

Sample Output:

[3, 5]
[-1, 0]
[3, 3]

Explanation:

Here is a breakdown of the above Python code:

The function "search_Range()" finds the range of indices for a target value in a sorted list.
It initializes an empty list 'result_arra' to store the result.
It initializes variables 'start_pos' and 'end_pos'.
It iterates through the list using a for loop.
If the current element is equal to the target value and 'start_pos' is -1, it sets 'start_pos' and 'end_pos' to the current index.
If the current element is equal to the target value and 'start_pos' is not -1, it updates 'end_pos' to the current index.
It appends 'start_pos' and 'end_pos' to the result list.
It returns the result list.
Test the function with different lists and target values, and print the results.

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to locate the first and last occurrence of a target value in a sorted array using binary search.
Write a Python program to return the index range where a given value appears in an ascending list.
Write a Python program to identify the starting and ending positions of a target element in a sorted array.
Write a Python program to determine the index boundaries for a given target in a sorted list, returning [-1, 0] if not found.

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