You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.
"""
File: binary_search_edge.py
Created Time: 2023-08-04
Author: Krahets (krahets@163.com)
"""
import sys , os . path as osp
sys . path . append ( osp . dirname ( osp . dirname ( osp . abspath ( __file__ ) ) ) )
from binary_search_insertion import binary_search_insertion
def binary_search_left_edge ( nums : list [ int ] , target : int ) - > int :
""" 二分查找最左一个 target """
# 等价于查找 target 的插入点
i = binary_search_insertion ( nums , target )
# 未找到 target ，返回 -1
if i == len ( nums ) or nums [ i ] != target :
return - 1
# 找到 target ，返回索引 i
return i
def binary_search_right_edge ( nums : list [ int ] , target : int ) - > int :
""" 二分查找最右一个 target """
# 转化为查找最左一个 target + 1
i = binary_search_insertion ( nums , target + 1 )
# j 指向最右一个 target ，
j = i - 1
# 未找到 target ，返回 -1
if j == - 1 or nums [ j ] != target :
return - 1
# 找到 target ，返回索引 j
return j
""" Driver Code """
if __name__ == " __main__ " :
# 包含重复元素的数组
nums = [ 1 , 3 , 6 , 6 , 6 , 6 , 6 , 10 , 12 , 15 ]
print ( f " \n 数组 nums = { nums } " )
# 二分查找左边界和右边界
for target in [ 6 , 7 ] :
index = binary_search_left_edge ( nums , target )
print ( f " 最左一个元素 { target } 的索引为 { index } " )
index = binary_search_right_edge ( nums , target )
print ( f " 最右一个元素 { target } 的索引为 { index } " )
