Python Bisect: Find the index position of the last occurrence of a given number in a sorted list using Binary Search

Last update on April 23 2025 12:55:34 (UTC/GMT +8 hours)

6. Last Occurrence with Binary Search

Write a Python program to find the index position of the last occurrence of a given number in a sorted list using Binary Search (bisect).

Sample Solution:

Python Code:

from bisect import bisect_right   
def BinarySearch(a, x): 
    i = bisect_right(a, x) 
    if i != len(a)+1 and a[i-1] == x: 
        return (i-1) 
    else: 
        return -1 
nums = [1, 2, 3, 4, 8, 8, 10, 12] 
x = 8
num_position   = BinarySearch(nums, x) 
if num_position == -1: 
    print("not presetn!") 
else: 
    print("Last occurrence of", x, "is present at", num_position)

Sample Output:

Last occurrence of 8 is present at 5

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to find the index of the last occurrence of a target number in a sorted list using bisect_right and subtracting one.
• Write a Python script to implement a binary search that returns the last occurrence index of a duplicate target value in a sorted array.
• Write a Python program that uses bisect_right to identify the rightmost index of a target and then prints the index of its last occurrence.
• Write a Python function to locate the final occurrence of a given number in a sorted list and handle cases where the target is absent.

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• Python Bisect Exercises Home ↩
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