Largest Values From Labels
<p>You are given <code>n</code> item&#39;s value and label as two integer arrays <code>values</code> and <code>labels</code>. You are also given two integers <code>numWanted</code> and <code>useLimit</code>.</p>

<p>Your task is to find a subset of items with the <strong>maximum sum</strong> of their values such that:</p>

<ul>
	<li>The number of items is <strong>at most</strong> <code>numWanted</code>.</li>
	<li>The number of items with the same label is <strong>at most</strong> <code>useLimit</code>.</li>
</ul>

<p>Return the maximum sum.</p>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">values = [5,4,3,2,1], labels = [1,1,2,2,3], numWanted = 3, useLimit = 1</span></p>

<p><strong>Output:</strong> <span class="example-io">9</span></p>

<p><strong>Explanation:</strong></p>

<p>The subset chosen is the first, third, and fifth items with the sum of values 5 + 3 + 1.</p>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">values = [5,4,3,2,1], labels = [1,3,3,3,2], numWanted = 3, useLimit = 2</span></p>

<p><strong>Output:</strong> <span class="example-io">12</span></p>

<p><strong>Explanation:</strong></p>

<p>The subset chosen is the first, second, and third items with the sum of values 5 + 4 + 3.</p>
</div>

<p><strong class="example">Example 3:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">values = [9,8,8,7,6], labels = [0,0,0,1,1], numWanted = 3, useLimit = 1</span></p>

<p><strong>Output:</strong> <span class="example-io">16</span></p>

<p><strong>Explanation:</strong></p>

<p>The subset chosen is the first and fourth items with the sum of values 9 + 7.</p>
</div>

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

<ul>
	<li><code>n == values.length == labels.length</code></li>
	<li><code>1 &lt;= n &lt;= 2 * 10<sup>4</sup></code></li>
	<li><code>0 &lt;= values[i], labels[i] &lt;= 2 * 10<sup>4</sup></code></li>
	<li><code>1 &lt;= numWanted, useLimit &lt;= n</code></li>
</ul>
Greedy; Array; Hash Table; Counting; Sorting
class Solution {
public:
    int largestValsFromLabels(vector<int>& values, vector<int>& labels, int numWanted, int useLimit) {
        int n = values.size();
        vector<pair<int, int>> pairs(n);
        for (int i = 0; i < n; ++i) {
            pairs[i] = {-values[i], labels[i]};
        }
        sort(pairs.begin(), pairs.end());
        unordered_map<int, int> cnt;
        int ans = 0, num = 0;
        for (int i = 0; i < n && num < numWanted; ++i) {
            int v = -pairs[i].first, l = pairs[i].second;
            if (cnt[l] < useLimit) {
                ++cnt[l];
                ++num;
                ans += v;
            }
        }
        return ans;
    }
};