<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 solve(vector<int>& nums, int k){
        if(k == 0) return 0;
        set<int> st;
        int n = nums.size();
        int ind[n+1]; 
        fill(ind, ind + n + 1 , -1);
        int start = 0;
        int r = 0;
        int ans = 0;
        auto call = [&](){
            int j = 1e9;
            for(auto ele : st) j = min(j, ind[ele]);
            ans += j-start+1;
        };
        while(r <  n){
            st.insert(nums[r]);
            ind[nums[r]] = r;
           if(st.size() == k){
                call();
           }
            if(st.size() == k+1){
                int j = 1e9;
                for(auto ele : st) j = min(j, ind[ele]);
                start = j;
                st.erase(nums[start]);
                start++;
                call();
            }
           r++;
        }
        return ans;
    }


    int subarraysWithKDistinct(vector<int>& nums, int k) {
        return solve(nums, k);
    }
};
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