118. Pascal's Triangle

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        if (numRows == 0) return {};
        if (numRows == 1) return {{1}};
        
        vector<vector<int>> prevRows = generate(numRows - 1);
        vector<int> newRow(numRows, 1);
        
        for (int i = 1; i < numRows - 1; i++) {
            newRow[i] = prevRows.back()[i - 1] + prevRows.back()[i];
        }
        
        prevRows.push_back(newRow);
        return prevRows;
    }
};