<p>You are given an integer <code>n</code>.</p>

<p>Each number from <code>1</code> to <code>n</code> is grouped according to the sum of its digits.</p>

<p>Return <em>the number of groups that have the largest size</em>.</p>

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

<pre>
<strong>Input:</strong> n = 13
<strong>Output:</strong> 4
<strong>Explanation:</strong> There are 9 groups in total, they are grouped according sum of its digits of numbers from 1 to 13:
[1,10], [2,11], [3,12], [4,13], [5], [6], [7], [8], [9].
There are 4 groups with largest size.
</pre>

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

<pre>
<strong>Input:</strong> n = 2
<strong>Output:</strong> 2
<strong>Explanation:</strong> There are 2 groups [1], [2] of size 1.
</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 10<sup>4</sup></code></li>
</ul>

static std::unordered_map<int,int> answer1399 = [](){
    std::unordered_map<int,int> ans;
    std::unordered_map<int,int> groupCounts;
    for (int i=1; i <= 10000; ++i)
    {
        int tmp = i;
        int digitSum = 0;
        while (tmp)
        {
            digitSum += (tmp % 10);
            tmp /= 10;
        }
        groupCounts[digitSum]++;
        int maxCount = 0;
        int numGroupsWithMaxCount = 0;
        for (auto&& [_, count] : groupCounts)
        {
            if (count > maxCount)
            {
                maxCount = count;
                numGroupsWithMaxCount = 1;
            }
            else if (count == maxCount)
                ++numGroupsWithMaxCount;
        }
        ans[i] = numGroupsWithMaxCount;
    }
    return ans;
}();

class Solution {
public:
    int countLargestGroup(int n) {
        return answer1399[n];
    }
};
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