################## insertion sort ####################
""" Insertion algorithm: alist = [54,26,93,17,77,31,44,55,20] The sequence is divided into two parts, Start off a first number that is ordered, alist = [54, 26,93,17,77,31,44,55,20] The first round, the first and the last part of the second portion of the comparison, if it is a small exchange, alist = [26,54 93,17,77,31,44,55,20] Second round, the first and last for a comparison of the first portion, a second portion smaller exchanged, and then forward, and if needed a small exchange, So the total is to achieve after the first, and has been comparing the front from the back, knowing the end, Select sort and insertion sort comparison: Insertion sort is extracted from a second part, the first part from start to finish, and then to compare, and then inserted into, And selecting a different sort, selection sort is divided into two parts, but it is behind the comparison, comparing it to a minimum and then inserted to the rearmost portion of the first, which is selection sort, """
################## insertion sort ####################
# First Edition:
def insert_sort(alist):
n = len (alist)
for j in range(1,n):
i = j
while i>0:
if alist[i] < alist[i-1]:
alist[i],alist[i-1]= alist[i-1],alist[i]
i -=1
else:
break # without this one can, but can optimize the optimal time complexity for orderly queue, the complexity of the inner layer becomes 1, and
# second edition:
def insert_sort2(alist):
# From the second position, i.e., the elements labeled 1 start to be inserted forwardly
for i in range(1, len(alist)):
Comparison # i th element of from the start of forward, is less than the previous element, the exchange position
for j in range(i, 0, -1):
if alist[j] < alist[j-1]:
alist[j], alist[j-1] = alist[j-1], alist[j]
# The outer loop is to ensure that all elements are taken out of the second portion
# Inner loop is to ensure that the value taken out from the back comparison again, if small exchanged,
if __name__ == '__main__':
alist = [54,26,93,17,77,31,44,55,20]
print(alist)
insert_sort(alist)
print(alist)