To solve this problem, we can use the sliding window technique. Here are the steps:

1. Initialize two pointers, `start` and `end`, to the beginning of the string.
2. Create a dictionary, `char_count`, to keep track of the count of each character in the current substring.
3. Iterate over the string using the `end` pointer. For each character:
- Add the character to `char_count`.
- If the number of unique characters in `char_count` is greater than `K`, move the `start` pointer to the right until the number of unique characters is exactly `K`.
4. After each iteration, update the maximum length of the substring if the current substring is longer.
5. Continue this process until the `end` pointer reaches the end of the string.
6. The maximum length recorded is the length of the longest substring with exactly `K` unique characters.

Here is a Python code snippet that implements this algorithm:

```python
def longest_substring(s, k):
char_count = {}
start = 0
max_length = 0

for end in range(len(s)):
if s[end] not in char_count:
char_count[s[end]] = 0
char_count[s[end]] += 1

while len(char_count) k:
char_count[s[start]] -= 1
if char_count[s[start]] == 0:
del char_count[s[start]]
start += 1

max_length = max(max_length, end - start + 1)

return max_length
```

You can call this function with the string and `K` as arguments to get the length of the longest substring with exactly `K` unique characters. For example:

```python
print(longest_substring('aabacbebebe', 3)) # Output: 7
print(longest_substring('abbc', 1)) # Output: 2
```

This function works by maintaining a sliding window of characters that contains at most `K` unique characters, and continuously updates the maximum length of such a substring as it iterates over the string.

Question

To solve this problem, we can use the sliding window technique. Here are the steps:

1. Initialize two pointers, `start` and `end`, to the beginning of the string.
2. Create a dictionary, `char_count`, to keep track of the count of each character in the current substring.
3. Iterate over the string using the `end` pointer. For each character:
   - Add the character to `char_count`.
   - If the number of unique characters in `char_count` is greater than `K`, move the `start` pointer to the right until the number of unique characters is exactly `K`.
4. After each iteration, update the maximum length of the substring if the current substring is longer.
5. Continue this process until the `end` pointer reaches the end of the string.
6. The maximum length recorded is the length of the longest substring with exactly `K` unique characters.

Here is a Python code snippet that implements this algorithm:

```python
def longest_substring(s, k):
    char_count = {}
    start = 0
    max_length = 0

for end in range(len(s)):
        if s[end] not in char_count:
            char_count[s[end]] = 0
        char_count[s[end]] += 1

while len(char_count) > k:
            char_count[s[start]] -= 1
            if char_count[s[start]] == 0:
                del char_count[s[start]]
            start += 1

max_length = max(max_length, end - start + 1)

return max_length
```

You can call this function with the string and `K` as arguments to get the length of the longest substring with exactly `K` unique characters. For example:

```python
print(longest_substring('aabacbebebe', 3))  # Output: 7
print(longest_substring('abbc', 1))  # Output: 2
```

This function works by maintaining a sliding window of characters that contains at most `K` unique characters, and continuously updates the maximum length of such a substring as it iterates over the string.

Knowee AI · Accepted Answer

To solve this problem, we can use the sliding window technique. Here are the steps:

1. Initialize two pointers, `start` and `end`, to the beginning of the string.
2. Create a dictionary, `char_count`, to keep track of the count of each character in the current substring.
3. Iterate over the string using the `end` pointer. For each character:
   - Add the character to `char_count`.
   - If the number of unique characters in `char_count` is greater than `K`, move the `start` pointer to the right until the number of unique characters is exactly `K`.
4. After each iteration, update the maximum length of the substring if the current substring is longer.
5. Continue this process until the `end` pointer reaches the end of the string.
6. The maximum length recorded is the length of the longest substring with exactly `K` unique characters.

Here is a Python code snippet that implements this algorithm:

```python
def longest_substring(s, k):
    char_count = {}
    start = 0
    max_length = 0

for end in range(len(s)):
        if s[end] not in char_count:
            char_count[s[end]] = 0
        char_count[s[end]] += 1

while len(char_count) > k:
            char_count[s[start]] -= 1
            if char_count[s[start]] == 0:
                del char_count[s[start]]
            start += 1

max_length = max(max_length, end - start + 1)

return max_length
```

You can call this function with the string and `K` as arguments to get the length of the longest substring with exactly `K` unique characters. For example:

```python
print(longest_substring('aabacbebebe', 3))  # Output: 7
print(longest_substring('abbc', 1))  # Output: 2
```

This function works by maintaining a sliding window of characters that contains at most `K` unique characters, and continuously updates the maximum length of such a substring as it iterates over the string.

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