<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 answer = 0;
        int left = 0;
        map<int, int> freq, lastIndex;

        for(int i=0;i<nums.size();i++) {
            freq[nums[i]]++;
            lastIndex[nums[i]] = i;
            if(freq.size()<k) {
                continue;
            }
            if(freq.size()>k) {
                while(freq.size() > k) {
                    freq[nums[left]]--;
                    if(freq[nums[left]] == 0) {
                        freq.erase(nums[left]);
                        lastIndex.erase(nums[left]);
                    }
                    left++;
                }
            }
            int minIndex = i;
            for(auto i: lastIndex) {
                minIndex = min(minIndex, i.second);
            }
            
            answer+=minIndex-left+1;
            //cout << left << " " << minIndex << " " << i << " " << answer << endl;
        }
        return answer;
        
    }
};
63318