Pascal.java

// 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:

class Solution {
    public List<List<Integer>> generate(int numRows) {
        List<List<Integer>> ans = new ArrayList<>();
        for (int i = 0; i < numRows; i++) {
            List<Integer> row = new ArrayList<>();
            for (int j = 0; j <= i; j++) {
                if (j == 0 || j == i) {
                    row.add(1);
                } else {
                    row.add(ans.get(i - 1).get(j - 1) + ans.get(i - 1).get(j));
                }
            }
            ans.add(row);
        }
        return ans;
        
    }
}