我为什么要为此获得KeyError？

Question

问题是： 给定一个包含0和1s的数组，如果允许您用1s替换不超过“ K” 0，请找到具有所有1s的最长连续子阵列的长度。

输入：array = [0、1、1、0、0、0、1、1、0、1、1]，k = 2 输出：6 说明：在索引5和8处替换“ 0”，具有1s的最长连续子阵列，长度为6。

def length_of_longest_substring(arr, k):
    '''
    Create a hashmap that records the values of 0 and 1, initialize them to 0. Do a sliding 
    window.
    WHILE the frequency of 0 is greater than k, subtract arr[windowStart] from HM and then 
    increment 
    wS.
    Use the max function to record longest substring length. Return that.
    '''

    hm = {'0': '0', '1': '0'}
    (windowStart, longest) = (0, 0)
    for windowEnd in range(len(arr)):
        right = arr[windowEnd]
        hm[right] = hm.get(right, 0) + 1
        while hm["0"] > k:
            hm[arr[windowStart]] -= 1
            windowStart += 1
        longest = max(longest, windowEnd - windowStart + 1)
    return longest


def main():
    print(length_of_longest_substring([1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1], 2)) 
    #Return 6
    print(length_of_longest_substring([1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1], 3))
    #Return 9
main()

我在hm [hm [0“”]＆gt; k中遇到

File "main.py", line 12, in length_of_longest_substring
    while hm["0"] > k:
KeyError: 0

错误使用0开始索引。 我尝试了.get函数。我做了hm.get（“ 0”），同样的错误。 我希望while循环计算0。我该如何实现？预先感谢您，非常感谢。

Answer 1

我认为您在循环的中误解了逻辑。我已经对其进行了修改，并且错误已修复。

# While the frequency of 0 is greater than k, subtract arr[windowStart] from hm and then increment windowStart.
if hm[0] > k:
    hm[arr[windowStart]] -= 1
    windowStart += 1

# Record longest substring length.
longest = max(longest, windowEnd - windowStart + 1)

# Increment the frequency of arr[windowEnd] in hm.
hm[arr[windowEnd]] += 1

---

输出：

6
10

Answer 2

您正在比较整数，然后将str转换为int

注意：我不是在解决问题，而是根据问题的要求解决错误。

def length_of_longest_substring(arr, k):
    '''
    Create a hashmap that records the values of 0 and 1, initialize them to 0. Do a sliding 
    window.
    WHILE the frequency of 0 is greater than k, subtract arr[windowStart] from HM and then 
    increment 
    wS.
    Use the max function to record longest substring length. Return that.
    '''

    hm = {'0': '0', '1': '0'}
    (windowStart, longest) = (0, 0)
    for windowEnd in range(len(arr)):
        right = arr[windowEnd]
        hm[right] = hm.get(right, 0) + 1
        while (((int)(hm["0"])) > k):
            hm[arr[windowStart]] -= 1
            windowStart += 1
        longest = max(longest, windowEnd - windowStart + 1)
    return longest


def main():
    print(length_of_longest_substring([1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1], 2)) 
    #Return 6
    print(length_of_longest_substring([1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1], 3))
    #Return 9
main()