2780. Minimum Index of a Valid Split - Explanation

class Solution:
    def minimumIndex(self, nums: List[int]) -> int:
        n = len(nums)

        for i in range(n - 1):
            left_cnt = defaultdict(int)
            for l in range(i + 1):
                left_cnt[nums[l]] += 1

            right_cnt = defaultdict(int)
            for r in range(i + 1, n):
                right_cnt[nums[r]] += 1

            for num in left_cnt:
                if left_cnt[num] > (i + 1) // 2 and right_cnt[num] > (n - i - 1) // 2:
                    return i

        return -1

class Solution:
    def minimumIndex(self, nums: List[int]) -> int:
        left = defaultdict(int)
        right = Counter(nums)

        for i in range(len(nums)):
            left[nums[i]] += 1
            right[nums[i]] -= 1

            left_len = i + 1
            right_len = len(nums) - i - 1

            if 2 * left[nums[i]] > left_len and 2 * right[nums[i]] > right_len:
                return i

        return -1

class Solution:
    def minimumIndex(self, nums: List[int]) -> int:
        majority = count = 0
        for num in nums:
            if count == 0:
                majority = num
            count += (1 if majority == num else -1)

        left_cnt, right_cnt = 0, nums.count(majority)

        for i in range(len(nums)):
            if nums[i] == majority:
                left_cnt += 1
                right_cnt -= 1

            left_len = i + 1
            right_len = len(nums) - i - 1

            if 2 * left_cnt > left_len and 2 * right_cnt > right_len:
                return i

        return -1