[LeetCode] Pascal's Triangle

Problem: Given an integer numRows, return the first numRows of Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:

Example:

Input: numRows = 5
Output: [[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]]

Input: numRows = 1
Output: [[1]]

Approach: It's just simple implementation problem. Please have a look at implementation directly.

Implementation in C#:

    public IList<IList<int>> Generate(int numRows)

    {

        var result = new List<IList<int>>();

        if (numRows == 0)

        {

            return result;

        }

        result.Add(new List<int> {1});

        if (numRows == 1)

        {

            return result;

        }

        result.Add(new List<int> {1, 1});

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

        {

            var currRow = new List<int>();

            var lastRow = result[i - 1];

            currRow.Add(1);

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

            {

                currRow.Add(lastRow[j - 1] + lastRow[j]);

            }

            currRow.Add(1);

            result.Add(currRow);

        }

        return result;

    }

Complexity: O(n^2)