Zane Xu
6e4e45addc
实现二分查找算法 binary_search，包含测试函数 test_binary_search 支持各种边界情况测试 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
56 lines
1.4 KiB
Python
56 lines
1.4 KiB
Python
def binary_search(arr, target):
|
|
"""
|
|
二分查找算法
|
|
返回目标值在数组中的索引，如果不存在则返回 -1
|
|
"""
|
|
left, right = 0, len(arr) - 1
|
|
|
|
while left <= right:
|
|
mid = left + (right - left) // 2 # 防止溢出
|
|
|
|
if arr[mid] == target:
|
|
return mid
|
|
elif arr[mid] < target:
|
|
left = mid + 1
|
|
else:
|
|
right = mid - 1
|
|
|
|
return -1
|
|
|
|
|
|
def test_binary_search():
|
|
"""测试二分查找函数"""
|
|
test_cases = [
|
|
# (数组, 目标值, 期望索引)
|
|
([1, 2, 3, 4, 5], 3, 2),
|
|
([1, 2, 3, 4, 5], 1, 0),
|
|
([1, 2, 3, 4, 5], 5, 4),
|
|
([1, 2, 3, 4, 5], 0, -1),
|
|
([1, 2, 3, 4, 5], 6, -1),
|
|
([], 5, -1),
|
|
([5], 5, 0),
|
|
([5], 3, -1),
|
|
([1, 3, 5, 7, 9], 7, 3),
|
|
([1, 3, 5, 7, 9], 2, -1),
|
|
]
|
|
|
|
all_passed = True
|
|
for i, (arr, target, expected) in enumerate(test_cases):
|
|
result = binary_search(arr, target)
|
|
if result == expected:
|
|
print(f"测试用例 {i + 1} 通过: binary_search({arr}, {target}) = {result}")
|
|
else:
|
|
print(f"测试用例 {i + 1} 失败: binary_search({arr}, {target}) = {result}, 期望 {expected}")
|
|
all_passed = False
|
|
|
|
if all_passed:
|
|
print("所有测试用例通过!")
|
|
else:
|
|
print("部分测试用例失败!")
|
|
|
|
return all_passed
|
|
|
|
|
|
if __name__ == "__main__":
|
|
# 运行测试
|
|
test_binary_search() |