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 1:
Input: numRows = 5 Output: [[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]]
Example 2:
Input: numRows = 1 Output: [[1]]
Constraints:
1 <= numRows <= 30class Solution {
public List<List<Integer>> generate(int numRows) {
List<List<Integer>> tri = new ArrayList<>();
tri.add(List.of(1));
for (int i = 1; i < numRows; i++) {
List<Integer> row = new ArrayList<>();
row.add(1);
List<Integer> prev = tri.get(tri.size() - 1);
for (int j = 1; j < prev.size(); j++)
row.add(prev.get(j - 1) + prev.get(j));
row.add(1);
tri.add(row);
}
return tri;
}
}