如何在数组抖动中找到重复元素的长度？

def find_duplicate_length(arr):
    visited = set()
    start_idx = None
    end_idx = None

    for i in range(len(arr)):
        if arr[i] in visited:
            start_idx = arr.index(arr[i])
            end_idx = i
            break
        else:
            visited.add(arr[i])

    if start_idx is not None and end_idx is not None:
        return end_idx - start_idx + 1
    else:
        return 0

# 示例用法
arr = [1, 2, 3, 4, 5, 3, 6, 7, 8, 3, 9, 10]
result = find_duplicate_length(arr)
print(result)  # 输出：4（重复元素为3，长度为4）