<p>You are given an array of integers&nbsp;<code>nums</code>, there is a sliding window of size <code>k</code> which is moving from the very left of the array to the very right. You can only see the <code>k</code> numbers in the window. Each time the sliding window moves right by one position.</p>

<p>Return <em>the max sliding window</em>.</p>

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

<pre>
<strong>Input:</strong> nums = [1,3,-1,-3,5,3,6,7], k = 3
<strong>Output:</strong> [3,3,5,5,6,7]
<strong>Explanation:</strong> 
Window position                Max
---------------               -----
[1  3  -1] -3  5  3  6  7       <strong>3</strong>
 1 [3  -1  -3] 5  3  6  7       <strong>3</strong>
 1  3 [-1  -3  5] 3  6  7      <strong> 5</strong>
 1  3  -1 [-3  5  3] 6  7       <strong>5</strong>
 1  3  -1  -3 [5  3  6] 7       <strong>6</strong>
 1  3  -1  -3  5 [3  6  7]      <strong>7</strong>
</pre>

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

<pre>
<strong>Input:</strong> nums = [1], k = 1
<strong>Output:</strong> [1]
</pre>

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

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-10<sup>4</sup> &lt;= nums[i] &lt;= 10<sup>4</sup></code></li>
	<li><code>1 &lt;= k &lt;= nums.length</code></li>
</ul>

class Solution {
public:
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        std::map<int, std::size_t, std::greater<int>> window_elem_map;

        std::vector<int> result;
        result.reserve(nums.size()/k + 1);

        int right = std::min<int>(k, nums.size());

        // populate initial window
        for(std::size_t i=0; i < right; i++)
        {
            window_elem_map[nums[i]] += 1;
        }

        result.push_back(window_elem_map.begin()->first);
        right++;

        while(right <= nums.size()) {
            const int left = nums[right-k-1];

            std::size_t& count = window_elem_map[left];
            count -= 1;

            if(count == 0) {
                window_elem_map.erase(left);
            }

            window_elem_map[nums[right-1]] += 1;

            const int max_element = window_elem_map.begin()->first;
            result.push_back(max_element);

            right += 1;
        }


        return result;
    }
};
180086