Find the longest substring length satisfying the condition

Given a string S The rules of change : Swap characters at any two different positions in the string Input description ： A string of lowercase letters Output description ： Transform as required to get the minimum string example

Input  abcdef

Output abcdef

example 2：

Input bcdefa

Output acdefb

s Are all lowercase characters 1<=s.length<=1000

Their thinking ：
Violent solution , Convert string to list , One by one , Determine whether the current character is the remaining string （ Contain itself ） Minimum character of , If it is , Then proceed to the next ; If not , Then the position of the smallest character is recorded , And exchange the current character with the minimum character once ,break Can , Because it can only be exchanged once
 

str1=input()
i=0
list1=list(str1)
print(list1)
while i<len(list1):
    minchar=min(list1[i:])
    if list1[i]==minchar:
        i+=1
    else:
        tem=list1[i]
        location=list1.index(minchar)
        list1[i]=minchar
        list1[location]=tem

        break
print(''.join(list1))