Leetcode 1684 Solution

This article provides solution to leetcode question 1684 (find-latest-group-of-size-m)
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https://leetcode.com/problems/find-latest-group-of-size-m

Solution

class Solution:
    def findLatestStep(self, arr: List[int], m: int) -> int:
        n = len(arr)
        v = [-1] * n
        lens = collections.defaultdict(int)

        ans = -1
        for j, i in enumerate(arr):
            i -= 1

            if i > 0 and v[i - 1] != -1:
                left = v[i - 1]
                lens[i - left] -= 1
            else:
                left = i

            if i < n - 1 and v[i + 1] != -1:
                right = v[i + 1]
                lens[right - i] -= 1
            else:
                right = i

            v[left] = right
            v[right] = left
            lens[right - left + 1] += 1

            if lens[m] > 0:
                ans = max(ans, j)

        return ans + 1 if ans != -1 else -1