How to swap maximums with the minimums? (python)

问题:

Is there a method to swap the maximum and the minimum of a list?

The list will be as follows and the program has to be continued so that it will print the maximum swapped with the minimum, the second maximum swapped with the second minimum and third maximum swapped with the third minimum.

Eg. Enter input- 0 1 2 3 4 5 6 7 8 9 -1 Output- 9873456210

a = []
nums = raw_input("Enter input- ")
for n in nums.split():
    n = int(n)
    if n < 0:
        break
    a.append(n)
if len(a)<7:
    print "please enter more than 7 integers"

回答1:

There is no method for this in python. You can try using primitive methods to build what you want using lists.

This code does the job:

#!/usr/bin/python
a = []
b = []
nums = raw_input("Enter input- ")
#append all to a list
for n in nums.split():
    n = int(n)
    if n < 0:
        break
    a.append(n)

#get the maximums
b = list(a)
first_max = max(b)
b.remove(first_max)
second_max = max(b)
b.remove(second_max)
third_max = max(b)

#get the minimums
b = list(a)
first_min = min(b)
b.remove(first_min)
second_min = min(b)
b.remove(second_min)
third_min = min(b)

## now swap 
xMax, yMax, zMax = a.index(first_max), a.index(second_max), a.index(third_max)
xMin, yMin, zMin = a.index(first_min), a.index(second_min), a.index(third_min)
a[xMax], a[xMin] = a[xMin], a[xMax]
a[yMax], a[yMin] = a[yMin], a[yMax]
a[zMax], a[zMin] = a[zMin], a[zMax]

print a

回答2:

I assume the list contains no duplicate values. Then you can construct a new sorted list to find the lowest and highest numbers.

After that you take the corresponding values from the sorted list, find their index in the original list and swap them.

data = list(range(10))
helper = sorted(data)
for i in range(3):
    low_value = helper[i]
    high_value = helper[-(i+1)]
    low_index = data.index(low_value)
    high_index = data.index(high_value)
    print(low_index, high_index)
    data[low_index], data[high_index] = data[high_index], data[low_index]
print(data)

回答3:

Check this out.

>>> sorted(student_tuples, key=itemgetter(2), reverse=True)
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]