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[leetcode]Pascal's Triangle

Pascal‘s Triangle

 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]]

算法思路:

迭代:根据当前行,求出下一行

代码如下:

 1 public class Solution { 2   List<List<Integer>> result = new ArrayList<List<Integer>>(); 3     public List<List<Integer>> generate(int numRows) { 4         if(numRows <= 0) return result; 5         List<Integer> list = new ArrayList<Integer>(); 6         list.add(1); 7         for(int i = 0; i < numRows; i++){ 8             result.add(new ArrayList<Integer>(list)); 9             list = getNextRow(list);10         }11         return result;12     }13     private List<Integer> getNextRow(List<Integer> list){14         List<Integer> l = new ArrayList<Integer>();15         l.add(1);16         for(int i = 1 ; i < list.size(); l.add(list.get(i) + list.get(i - 1)),i++);17         l.add(1);18         return l;19     }20 }