Given numRows, generate the first numRows of Pascal‘s triangle.
For example, given numRows = 5,
Return
[
[1],
[1,1],
[1,2,1],
[1,3,3,1],
[1,4,6,4,1]
]
Key to the solution is to use two arrays, one for current list, one for previous array.
1 public class Solution { 2 public List<List<Integer>> generate(int numRows) { 3 List<List<Integer>> result = new ArrayList<List<Integer>>(); 4 if (numRows == 0) 5 return result; 6 List<Integer> prev = new ArrayList<Integer>(); 7 prev.add(1); 8 result.add(prev); 9 while (numRows > 1) { 10 List<Integer> current = new ArrayList<Integer>(); 11 int length = prev.size(); 12 current.add(1); 13 for (int i = 0; i < length - 1; i++) 14 current.add(prev.get(i) + prev.get(i + 1)); 15 current.add(1); 16 result.add(current); 17 prev = current; 18 numRows--; 19 } 20 return result; 21 } 22 }
原文：http://www.cnblogs.com/ireneyanglan/p/4799910.html