[LeetCode] 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]
]

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
       
        
 递归版本
        





 
        

        
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