<p>Given an integer array <code>nums</code> and an integer <code>k</code>, return <em>the number of <strong>good subarrays</strong> of </em><code>nums</code>.</p>

<p>A <strong>good array</strong> is an array where the number of different integers in that array is exactly <code>k</code>.</p>

<ul>
	<li>For example, <code>[1,2,3,1,2]</code> has <code>3</code> different integers: <code>1</code>, <code>2</code>, and <code>3</code>.</li>
</ul>

<p>A <strong>subarray</strong> is a <strong>contiguous</strong> part of an array.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,1,2,3], k = 2
<strong>Output:</strong> 7
<strong>Explanation:</strong> Subarrays formed with exactly 2 different integers: [1,2], [2,1], [1,2], [2,3], [1,2,1], [2,1,2], [1,2,1,2]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,1,3,4], k = 3
<strong>Output:</strong> 3
<strong>Explanation:</strong> Subarrays formed with exactly 3 different integers: [1,2,1,3], [2,1,3], [1,3,4].
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 2 * 10<sup>4</sup></code></li>
	<li><code>1 &lt;= nums[i], k &lt;= nums.length</code></li>
</ul>

class Solution {
public:

    int cntlessthank(vector<int>nums, int k){
        int cntdist = 0;
        map<int,int>mp;
        for(auto x:nums)mp[x] = 0;
        int head = -1;
        int tail= 0;
        int ans = 0;
        int n =nums.size();
        while(tail<n){
            while(head+1<n and (cntdist<k || (cntdist==k and mp[nums[head+1]]>0))){
                head++;
                if(mp[nums[head]]==0){
                    cntdist++;
                }
                mp[nums[head]]++;
            }
            ans+=(head-tail+1);
            if(tail<=head){
                mp[nums[tail]]--;
                if(mp[nums[tail]]==0){
                    cntdist--;
                }
                tail++;
            }else{
                tail++;
                head=tail-1;
            }
        }
        return ans;
    }

    int subarraysWithKDistinct(vector<int>& nums, int k) {
       
        return cntlessthank(nums,k)-cntlessthank(nums,k-1);
    }
};
57085