<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:
    //好題目,學習讓預設sort函數幫我們自動排序(按照參數順序)
    vector<int> findDiagonalOrder(vector<vector<int>>& nums) {
        ios_base::sync_with_stdio(0);
        cin.tie(NULL);
        cout.tie(NULL);

        int n = nums.size(), limit;
        vector<tuple<int,int,int>> data;
        for(int row = 0; row < n; ++row) {
            for(int col = 0; col < nums[row].size(); ++col) {
                data.push_back({row + col, col, row});
            }
        }
        //預設是小到大,遞增排序(less)
        sort(data.begin(),data.end());

        limit = data.size();
        vector<int> answer(limit);
        for(int i = 0; i < limit; ++i) {
            answer[i] = nums[get<2>(data[i])][get<1>(data[i])];
        }
        return answer;
    }
};
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