LeetCode OJ 118. 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]
]

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【思路】

这道题目很简单，代码如下：

 public class Solution {
     public List<List<Integer>> generate(int numRows) {
         List<List<Integer>> Pascal = new ArrayList<>();
         if(numRows == 0) return Pascal;
         List<Integer> list = new ArrayList<>();
         list.add(1);
         Pascal.add(list);
         if(numRows == 1) return Pascal;

         for(int i = 1; i < numRows; i++){
             list = new ArrayList<>();
             list.add(1);
             List<Integer> prelist = Pascal.get(i-1);
             int prelen = prelist.size();
             for(int j = 0; j < prelen - 1; j++){
                 list.add(prelist.get(j) + prelist.get(j+1));
             }
             list.add(1);
             Pascal.add(list);
         }
         return Pascal;
     }
 }