# PYTHON Programming for Write a program to print all permutations of a given string

PYTHON Programming for Write a program to print all permutations - Mathematical Algorithms - A permutation, also called an “arrangement number” or “order"

A permutation, also called an “arrangement number” or “order,” is a rearrangement of the elements of an ordered list S into a one-to-one correspondence with S itself. A string of length n has n! permutation.
Source: Mathword.

Below are the permutations of string ABC ABC ACB BAC BCA CBA CAB

Here is a solution that is used as a basis in backtracking.

Python
# Python program to print all permutations with
# duplicates allowed

def toString(List):
return ''.join(List)

# Function to print permutations of string
# This function takes three parameters:
# 1. String
# 2. Starting index of the string
# 3. Ending index of the string.
def permute(a, l, r):
if l==r:
print toString(a)
else:
for i in xrange(l,r+1):
a[l], a[i] = a[i], a[l]
permute(a, l+1, r)
a[l], a[i] = a[i], a[l] # backtrack

# Driver program to test the above function
string = "ABC"
n = len(string)
a = list(string)
permute(a, 0, n-1)

Output:

ABC
ACB
BAC
BCA
CBA
CAB

Backtracking
Time Complexity: O(n*n!) Note that there are n! permutations and it requires O(n) time to print a a permutation.

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