LeetCode - Pascal's Triangle II | Darren's Blog

Given an index k, return the k-th row of the Pascal's triangle. For example, given k = 3, return [1,3,3,1]
Note: Could you optimize your algorithm to use only O(k) extra space?

public List<Integer> getRow(int rowIndex) {

        if (rowIndex < 0)

            return null;

 

        List<Integer> result = new ArrayList<Integer>(rowIndex+1);

        result.add(1);

 

        // Build each row one at a time

        for (int i = 1; i <= rowIndex; i++) {

            int temp1 = 1;      // Leading 1

            for (int j = 1; j < i; j++) {

                int temp2 = result.get(j);  // Cache the value before it is overwritten

                result.set(j, temp1+temp2);

                temp1 = temp2;

            }

            result.add(1);      // Trailing 1

        }

 

        return result;

    }

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