在有序列表中查找最接近的值

def find_closest_value(arr, target):
    left, right = 0, len(arr) - 1
    closest = arr[left]
    
    while left <= right:
        mid = (left + right) // 2
        if abs(arr[mid] - target) < abs(closest - target):
            closest = arr[mid]
        
        if arr[mid] == target:
            return arr[mid]
        elif arr[mid] < target:
            left = mid + 1
        else:
            right = mid - 1
    
    return closest

# 示例用法
arr = [1, 3, 5, 7, 9]
target = 6
print(find_closest_value(arr, target))  # 输出: 5