[LeetCode] Pascal & amp; #39; s Triangle

[LeetCode] Pascal & #39; 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]]

Iterative non-recursive version

Public class Solution {public List
 
  
> Generate (int numRows) {List
  
   
> Res = new ArrayList <> (); if (numRows <= 0) return res; List
   
    
Lin = new ArrayList <> (); lin. add (1); res. add (lin); if (numRows = 1) return res; for (int I = 0; I
    
     
List = new ArrayList <> (); List
     
      
Pre = res. get (I); list. add (1); for (int j = 0; j
      

Recursive version
public class Solution {List
        
         > res = new ArrayList<>();    public List
         
          > generate(int numRows) {    if(numRows<=0) return res;    helpGenerate(numRows);    return res;    }        private List
          
            helpGenerate(int numRows){    if(numRows == 1){    List
           
             list = new ArrayList<>();    list.add(1);    res.add(list);    return list;    }    List
            
              pre = helpGenerate(numRows-1);    List
             
               list = new ArrayList<>(); list.add(1); for(int i=0;i