<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 subarraysWithKDistinct(vector<int>& nums, int k) {
        int n=nums.size();
        int left=0, right=-1, atleast_k=0, unique=0;
        unordered_map<int,int> cMap;
        for(auto x:nums)
        cMap[x]=0;
        while(right<n)
        {
            if(unique==k)
            {
                atleast_k+=(n-right);
                cMap[nums[left]]--;
                if(cMap[nums[left]]==0)
                unique--;
                left++;
            }
            else
            {
                right++;
                if(right<n)
                {
                    cMap[nums[right]]++;
                    if(cMap[nums[right]]==1)
                    unique++;
                }
            }
        }
        left=0; right=-1; unique=0;
        int atleast_k1=0;
        for(auto x:nums)
        cMap[x]=0;
        while(right<n)
        {
            if(unique==k+1)
            {
                atleast_k1+=(n-right);
                cMap[nums[left]]--;
                if(cMap[nums[left]]==0)
                unique--;
                left++;
            }
            else
            {
                right++;
                if(right<n)
                {
                    cMap[nums[right]]++;
                    if(cMap[nums[right]]==1)
                    unique++;
                }
            }
        }
        return (atleast_k-atleast_k1);
    }
};
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