给定一个列表，产生新列表，以列表的第一个数L(0)作为分界点产生新列表
L = [8,2,7,90,12,24,1]
left = [i for i in L if i < L[0]]
right = [i for i in L if i > L[0]]
new = left + [L[0]] + right
L = [8,2,7,90,12,24,1]
left = [i for i in L if i < L[0]]
right = [i for i in L if i > L[0]]
new = left + [L[0]] + right