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class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        vector<vector<int>> ans(numRows);
        for(int i = 1; i <= numRows; i++)
        {
            vector<int> tmp(i);
            if(i == 1)
            {
                tmp[0] = 1;
                ans[i-1] = tmp;
                continue;
            }
            if(i == 2)
            {
                tmp[0] = 1;
                tmp[1] = 1;
                ans[i-1] = tmp;
                continue;
            }
            tmp[0] = 1;
            tmp[i-1] = 1;
            for(int j = 1; j < i-1; j++)
            {
                tmp[j] = ans[i-2][j-1] + ans[i-2][j];
            }
            ans[i-1] = tmp;
        }
        return ans;
    }
};