Leetcode: Triangle @Python

class Solution:
    # @param triangle, a list of lists of integers
    # @return an integer
    def minimumTotal(self, triangle):
        n=len(triangle)
        if n==0:return 0
        sv=[triangle[0][0]]
        for i in range(1,n):# given sv for row i, calculate sv for row i+1
            new_sum=[0 for x in range(i+1)]
            for j in range(i+1):
                if j==0:
                    new_sum[0]=triangle[i][0]+sv[0]
                elif j==i:
                    new_sum[i]=triangle[i][i]+sv[i-1]
                else:
                    new_sum[j]=min(triangle[i][j]+sv[j-1],triangle[i][j]+sv[j])
            sv=new_sum[:]
        return min(sv)