992. Subarrays with K Different Integers Hard, 2 pointers
atmost(k) - atmost(k - 1) method
Approach
atMost concept used here.- using 2 pointer we cant find the exact thing, for that we have to tweak something like
atMost(k) - atMost(k - 1)
- for better visualization, check comments.
Code
```cpp
int atMost(const vector &nums, const int &k) {
if (k == 0)
return 0;
map<int, int> mp;
int left = 0, right = 0, ans = 0;
for (int right = 0; right < nums.size(); right++) {
mp[nums[right]]++;
while (left <= right and mp.size() > k) {
mp[nums[left]]--;
if (mp[nums[left]] == 0)
mp.erase(mp.find(nums[left]));
left++;
}
ans += (right - left + 1);
}
return ans;
}
int subarraysWithKDistinct(vector &nums, int k) {
return atMost(nums, k) - atMost(nums, k - 1);
}
```
</details>