<p>Given a 2D integer array <code>nums</code>, return <em>all elements of </em><code>nums</code><em> in diagonal order as shown in the below images</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/04/08/sample_1_1784.png" style="width: 158px; height: 143px;" />
<pre>
<strong>Input:</strong> nums = [[1,2,3],[4,5,6],[7,8,9]]
<strong>Output:</strong> [1,4,2,7,5,3,8,6,9]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/04/08/sample_2_1784.png" style="width: 230px; height: 177px;" />
<pre>
<strong>Input:</strong> nums = [[1,2,3,4,5],[6,7],[8],[9,10,11],[12,13,14,15,16]]
<strong>Output:</strong> [1,6,2,8,7,3,9,4,12,10,5,13,11,14,15,16]
</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>1 &lt;= nums[i].length &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= sum(nums[i].length) &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= nums[i][j] &lt;= 10<sup>5</sup></code></li>
</ul>


class Solution {
public:
    struct sumRowNum{
        int sum;
        int col;
        int val;

        bool operator>(const sumRowNum& other) const
        {
            if(sum == other.sum)
                return col > other.col;
            return sum > other.sum;
        }
    };
    vector<int> findDiagonalOrder(vector<vector<int>>& nums) {
        priority_queue<sumRowNum,vector<sumRowNum>,greater<sumRowNum>> pq;
        for(int i=0;i<nums.size();i++)
        {
            for(int j=0;j<nums[i].size();j++)
            {
                sumRowNum w;
                w.sum = i+j;
                w.col = j;
                w.val = nums[i][j];
                pq.push(w);
            }
        }

        vector<int> res;
        while(!pq.empty())
        {
            res.push_back(pq.top().val);
            pq.pop();
        }
        return res;
    }   
};
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