<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>& s, int k) {
        int n = s.size();
        int result = 0;
        int i = 0, portfolio_start = -1;
        unordered_map<int,int> umap;
        for(int j=0;j<n;j++) {
            umap[s[j]]++;
            while(umap.size() > k) {
                portfolio_start = -1;
                if(--umap[s[i]] == 0)
                    umap.erase(s[i]);
                i++;
            }
            if(umap.size() == k) {
                if(portfolio_start == -1)
                    portfolio_start = i;
                while(i < j and umap[s[i]] > 1)
                    umap[s[i++]]--;
                result += (i-portfolio_start+1);
            }
        }
        return result;
    }
};

//             l
// 1   2   1   2   3
//                 r
// *

// 1,2 .
// 2,1 .
// 1,2 .
// 2,3
// 1,2,1 .
// 2,1,2 .
// 1,2,1,2 .
47736