118. Pascal's Triangle

class Solution(object):
    def generate(self, n):
        """
        :type numRows: int
        :rtype: List[List[int]]
        """
        if n==0:
            return []
        if n==1:
            return [[1]]
        res=[[1],[1,1]]
        for i in range(3,n+1):
            templ=[]
            if i%2==0:
                end=i/2
                while end-1:
                    templ.append(res[i-1-1][-1*end]+res[i-1-1][1-end])
                templ.append(1)
                templ.reverse()
                templ.extend(templ[::-1])
                
                
            else:
                end=(i//2)+1
                while end-1:
                    templ.append(res[i-1-1][-1*end]+res[i-1-1][1-end])
                templ.append(1)
                templ.reverse()
                templ.extend(templ[:-end+1:])
            res.append(templ)
            return res

def generate(self, numRows):
        res = [[1]]
        for i in range(1, numRows):
            res += [map(lambda x, y: x+y, res[-1] + [0], [0] + res[-1])]
        return res[:numRows]

class Solution(object):
    def generate(self, numRows):
        a=[]
        for i in range(numRows):
            a.append([1]*(i+1))
            if i>1:
                for j in range(1,i):
                    a[i][j]=a[i-1][j-1]+ a[i-1][j]
        return a