1355. Yang Hui triangle

1355. Yang Hui triangle

Chinese English

Given a non-negative integer * numRows, * generates the first numRows  row of Yang Hui triangle  .

In the Yang Hui triangle, each number is the sum of its upper left and upper right numbers.

Sample

Example 1:

输入: 5
输出:
[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

Example 2:

输入: 3
输出:
[
     [1],
    [1,1],
   [1,2,1]
]

 

 

Enter test data (one parameter per line) How to understand test data?

class Solution:
     "" "
     @param numRows: num of rows 
    @return: generate Pascal ' s triangle 
    " ""
     ' ''
     General idea:
     1. First give the initial value res = [[ 1 ], [ 1 , 1 ]] And then start looping from the previous list to get the value and give a method to get the next list.
    '' '
     def generate (self, numRows): 
        res = [[ 1 ]]
         for i in range (numRows- 1 ): 
            res.append (self.getnextlist (res [i])) 
        return res 
        

    def getnextlist (self, pre_l ):1]
        for i in range(len(pre_l)-1): 
            l.append(pre_l[i]+pre_l[i+1])
        return l + [1]