 # Python Program to Check if Array can be Sorted with One Swap

In the previous article, we have discussed Python Program for Maximum Distance between Two Occurrences of Same Element in Array/List
Given a list and the task is to check to see if the given list can be sorted with a single swap.

copy() method:

The list’s shallow copy is returned by the copy() method.

There are no parameters to the copy() method.

It creates a new list. It makes no changes to the original list.

Examples:

Example1:

Input:

Given List = [7, 8, 9]

Output:

The given list [7, 8, 9] can be sorted with a single swap

Explanation:

When we swap 7 and 9 we get [9, 8, 7] which is a sorted list.

Example2:

Input:

Given List = [6, 3, 2, 1]

Output:

The given list [6, 3, 2, 1] cannot be sorted with a single swap

## Program to Check if Array can be Sorted with One Swap in Python:

Below are the ways to check to see if the given list can be sorted with a single swap.

### Method #1: Using For Loop (Static Input)

Approach:

• Give the list as static input and store it in a variable.
• Copy the given list in a variable say “new_lst” using the copy() function.
• Take a variable say ‘c’ and initialize its value with 0.
• Sort the above obtained “new_lst”.
• Loop until the length of the “new_lst” using the for loop.
• Check if the given list element is not equal to the new_lst element using the if conditional statement.
• If the statement is true then increment the count value of ‘c’ by 1 and store it in the same variable ‘c‘.
• Check if the value of ‘c’ is equal to 0 or true using the if conditional statement and ‘or ‘ keyword.
• If the statement is true, print “The given list can be sorted with a single swap”.
• If it is false, then print “The given list cannot be sorted with a single swap”.
• The Exit of the Program.

Below is the implementation:

# Give the list as static input and store it in a variable.
gven_lst = [7, 8, 9]
# Copy the given list in a variable say "new_lst" using the copy() function.
new_lst = gven_lst.copy()
# Take a variable say 'c' and initialize its value with 0.
c = 0
# Sort the above obtained "new_lst".
new_lst.sort()
# Loop until the length of the "new_lst" using the for loop.
for i in range(len(new_lst)):
# Check if the given list element is not equal to the new_lst element using the
# if conditional statement.
if(gven_lst[i] != new_lst[i]):
# If the statement is true then increment the count value of 'c' by 1 and
# store it in the same variable 'c'.
c += 1
# Check if the value of 'c' is equal to 0 or true using the if conditional statement
# and 'or ' keyword.
if(c == 0 or c == 2):
# If the statement is true, print "The given list can be sorted with a single swap".
print("The given list", gven_lst, "can be sorted with a single swap")
# If it is false, then print "The given list cannot be sorted with a single swap".
else:
print("The given list", gven_lst, "cannot be sorted with a single swap")


Output:

The given list [7, 8, 9] can be sorted with a single swap

### Method #2: Using For loop (User Input)

Approach:

• Give the list as user input using list(),map(),input(),and split() functions.
• Store it in a variable.
• Copy the given list in a variable say “new_lst” using the copy() function.
• Take a variable say ‘c’ and initialize its value with 0.
• Sort the above obtained “new_lst”.
• Loop until the length of the “new_lst” using the for loop.
• Check if the given list element is not equal to the new_lst element using the if conditional statement.
• If the statement is true then increment the count value of ‘c’ by 1 and store it in the same variable ‘c‘.
• Check if the value of ‘c’ is equal to 0 or true using the if conditional statement and ‘or ‘ keyword.
• If the statement is true, print “The given list can be sorted with a single swap”.
• If it is false, then print “The given list cannot be sorted with a single swap”.
• The Exit of the Program.

Below is the implementation:

# Give the list as user input using list(),map(),input(),and split() functions.
#Store it in a variable.
gven_lst = list(map(int, input(
'Enter some random List Elements separated by spaces = ').split()))
# Copy the given list in a variable say "new_lst" using the copy() function.
new_lst = gven_lst.copy()
# Take a variable say 'c' and initialize its value with 0.
c = 0
# Sort the above obtained "new_lst".
new_lst.sort()
# Loop until the length of the "new_lst" using the for loop.
for i in range(len(new_lst)):
# Check if the given list element is not equal to the new_lst element using the
# if conditional statement.
if(gven_lst[i] != new_lst[i]):
# If the statement is true then increment the count value of 'c' by 1 and
# store it in the same variable 'c'.
c += 1
# Check if the value of 'c' is equal to 0 or true using the if conditional statement
# and 'or ' keyword.
if(c == 0 or c == 2):
# If the statement is true, print "The given list can be sorted with a single swap".
print("The given list", gven_lst, "can be sorted with a single swap")
# If it is false, then print "The given list cannot be sorted with a single swap".
else:
print("The given list", gven_lst, "cannot be sorted with a single swap")


Output:

Enter some random List Elements separated by spaces = 5 6 7 12 15
The given list [5, 6, 7, 12, 15] can be sorted with a single swap

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