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;
    }
}