Implement repeated, which takes in an iterator t and returns the first value in t that appears k times in a row.Your implementation should iterate through the items in a way such that if the same iterator is passed into repeated twice, it should continue in the second call at the point it left off in the first.
时间: 2024-02-14 10:05:26 浏览: 31
Sure, here's a possible implementation of the `repeated` function in Python using a generator:
```python
def repeated(t, k):
last = None
count = 0
for item in t:
if item == last:
count += 1
if count == k:
return item
else:
last = item
count = 1
yield item
```
The `repeated` function takes two arguments: `t` is the iterator we want to search for repeated values, and `k` is the number of times a value must appear in a row to be considered repeated. The function initializes a `last` variable to `None` to keep track of the last value seen, and a `count` variable to 0 to keep track of the number of times the last value has been seen in a row. The function iterates over the items in `t` and yields each item. If the current item is equal to the last item (`item == last`), the `count` variable is incremented. If the `count` variable reaches `k`, the function returns the current item (i.e., we have found a repeated value). Otherwise, the `last` variable is updated to the current item and the `count` variable is reset to 1.
Importantly, the function uses `yield` instead of `return` to allow the caller to resume iteration from where it left off in the iterator. This means that if the same iterator is passed into `repeated` twice, the second call will continue iterating from where the first call left off, rather than starting over. For example:
```python
it = iter([1, 2, 3, 3, 3, 4, 4, 5, 5, 5, 5])
print(repeated(it, 3)) # Output: 3
print(list(it)) # Output: [4, 4, 5, 5, 5, 5]
print(repeated(it, 2)) # Output: 5
```
In the above example, we first create an iterator `it` over a list with repeated values. We then call `repeated(it, 3)` to search for a value that appears 3 times in a row, and it returns 3. We then print the remaining values in `it` by calling `list(it)`, which gives `[4, 4, 5, 5, 5, 5]`. Finally, we call `repeated(it, 2)` to search for a value that appears 2 times in a row, and it returns 5.