LeetCode - Pascal's Triangle | Darren's Blog

Given numRows, generate the first numRows of Pascal's triangle.
Each list p is generated by its previous list q . Except for the first and the last element,p[i]=q[i−1]+q[i]

public List<List<Integer>> generate(int numRows) {

        List<List<Integer>> result = new ArrayList<List<Integer>>();

        if (numRows == 0)

            return result;

 

        // Generate the first list

        List<Integer> previous = new ArrayList<Integer>(1);

        previous.add(1);

        result.add(previous);

 

        // A new list is generated base on its previous list

        for (int i = 2; i <= numRows; i++) {

            List<Integer> current = new ArrayList<Integer>(i);

            current.add(1);

            for (int j = 1; j < previous.size(); j++)

                current.add(previous.get(j-1) + previous.get(j));

            current.add(1);

            result.add(current);

            previous = current;

        }

 

        return result;

    }

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