_119.java

package com.fishercoder.solutions;

import java.util.ArrayList;
import java.util.List;

public class _119 {

    public static class Solution1 {
        public List<Integer> getRow(int rowIndex) {
            if (rowIndex < 0) {
                return new ArrayList();
            }
            List<List<Integer>> result = new ArrayList();
            List<Integer> row = new ArrayList();
            row.add(1);
            result.add(row);
            for (int i = 1; i <= rowIndex; i++) {
                List<Integer> newRow = new ArrayList();
                newRow.add(1);
                List<Integer> lastRow = result.get(i - 1);
                for (int j = 1; j < lastRow.size(); j++) {
                    newRow.add(lastRow.get(j - 1) + lastRow.get(j));
                }
                newRow.add(1);
                result.add(newRow);
            }
            return result.get(result.size() - 1);
        }
    }

    public static class Solution2 {
        /**
         * O(k) space
         */
        public List<Integer> getRow(int rowIndex) {
            List<Integer> row = new ArrayList<>();
            for (int i = 0; i <= rowIndex; i++) {
                row.add(0, 1);
                for (int j = 1; j < row.size() - 1; j++) {
                    row.set(j, row.get(j) + row.get(j + 1));
                }
            }
            return row;
        }
    }
}