<p>Given an integer <code>numRows</code>, return the first numRows of <strong>Pascal&#39;s triangle</strong>.</p>

<p>In <strong>Pascal&#39;s triangle</strong>, each number is the sum of the two numbers directly above it as shown:</p>
<img alt="" src="https://upload.wikimedia.org/wikipedia/commons/0/0d/PascalTriangleAnimated2.gif" style="height:240px; width:260px" />
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> numRows = 5
<strong>Output:</strong> [[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> numRows = 1
<strong>Output:</strong> [[1]]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= numRows &lt;= 30</code></li>
</ul>

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<int>prev={1};
        vector<int>curr={1,1};
        vector<vector<int>> sol;

        if(numRows==1){
            sol.push_back(prev);
            return sol;
        }
        if(numRows==2){
            sol.push_back(prev);
            sol.push_back(curr);
            return sol;
        }

        sol.push_back(prev);
        sol.push_back(curr);

        while(numRows>2){
            vector<int>newRow;

            newRow.push_back(1);
            for(int i=0;i<curr.size()-1;i++){
                newRow.push_back(curr[i]+curr[i+1]);
            }
            newRow.push_back(1);

            curr=newRow;
            sol.push_back(newRow);
            --numRows;
        }

        return sol;
    }
};
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