Question

所以我编写了一个二进制搜索算法，但是当我进行测试运行时，它并不能很好地工作。

这是代码

val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(e => {
     |    println("e =" + e)
     |    (e._2)
     | })
e =(a,List((1,11), (1,111)))
e =(b,List((2,22), (2,222)))
ys: scala.collection.immutable.Map[Int,Int] = Map(1 -> 111, 2 -> 222)

abd这里是调用函数的代码

def binarySearch(lst, target):
    low = 0
    high = len(lst)-1
    while high >= low:
        mid = (high + low)//2
        if target < lst[mid]:
           high = mid - 1
        elif target > lst[mid]:
            low = mid + 1
        else:
            return mid

    return (-1 * (mid+1))

问题是这样，我想在实际运行它给出的函数时将列表target_values添加到第一个正确的顺序

lst_test = [3, 4, 6, 7]
target_values = [1, 3, 5, 8]

for t in target_values:
    i = binarySearch(lst_test, t)
    if (i < 0):
        print("In", lst_test, t, "is going to be inserted at index",-1*(i+1))
        lst_test.insert((i+1)*-1, t)
    else:
        print("In", lst_test, t, "was found at index", i)
print("The final list is:", lst_test)

这很奇怪，它的工作却只在通话的最后部分失败了有什么方法可以解决这个问题吗？最终名单应为[1,3,4,5,6,7,8]

根据要求，我跟踪了我的二进制搜索算法，它的质量很差。我希望这会有所帮助

In [3, 4, 6, 7] 1 is going to be inserted at index 0
In [1, 3, 4, 6, 7] 3 was found at index 1
In [1, 3, 4, 6, 7] 5 is going to be inserted at index 3
In [1, 3, 4, 5, 6, 7] 8 is going to be inserted at index 5
The final list is: [1, 3, 4, 5, 6, 8, 7]

Answer 1

只需更改函数即可返回<div id="LoggedAs"><span><?php echo $user_ip;?></span></div>：

(-1 * (low+1))

输出：

def binarySearch(lst, target):
    low = 0
    high = len(lst)-1
    while high >= low:
        mid = (high + low)//2
        if target < lst[mid]:
           high = mid - 1
        elif target > lst[mid]:
           low = mid + 1
        else:
           return mid

    return (-1 * (low+1))

原始实现的问题是代码假定('In', [3, 4, 6, 7], 1, 'is going to be inserted at index', 0) ('In', [1, 3, 4, 6, 7], 3, 'was found at index', 1) ('In', [1, 3, 4, 6, 7], 5, 'is going to be inserted at index', 3) ('In', [1, 3, 4, 5, 6, 7], 8, 'is going to be inserted at index', 6) ('The final list is:', [1, 3, 4, 5, 6, 7, 8])是插入索引，但它永远不会超出循环中的当前列表，因为它应该在将值插入列表末尾时使用。

Answer 2

我想我明白了。加入我推荐的印刷语句。跟踪现有列表末尾的插入。我相信你会发现你无法驱动低高到足以引发列表末尾的插入;你能得到的最多就是在最后一个元素之前插入，这正是你的测试中发生的事情。

二进制搜索算法不起作用

2 个答案: