在Python中打印字符串的所有子序列

给定一个字符串，我们必须找出它的所有子序列。字符串是给定字符串的子序列，它是通过删除给定字符串的某些字符而不更改其顺序而生成的。
例子：

Input : abc
Output : a, b, c, ab, bc, ac, abc

Input : aaa
Output : a, aa, aaa

使用挑选和不挑选的概念：

Python3

def printSubSequences(STR, subSTR=""):
    """
    function:
        To print all subsequences of string
        concept:
            Pick and Don’t Pick
        variables:
            STR = string
            subSTR = to store subsequence
    """
    if len(STR) == 0:
        print(subSTR, end=" ")
        return
 
    # we add adding 1st character in string
    printSubSequences(STR[:-1], subSTR + STR[-1])
    """
    Not adding first character of the string
    because the concept of subsequence either
    character will present or not
    """
    printSubSequences(STR[:-1], subSTR)
    return
 
 
def main():
    """
    main function to drive code
    """
    STR = "abc"
    printSubSequences(STR)
 
 
if __name__ == "__main__":
    main()
 
# by itsvinayak

输出：

cba cb ca c ba b a  

蟒蛇实现：

先决条件： Python中的 itertools.combinations() 模块打印所有可能的组合

Python3

# Python Implementation of the approach
import itertools
 
def Sub_Sequences(STR):
    combs = []
    for l in range(1, len(STR)+1):
        combs.append(list(itertools.combinations(STR, l)))
    for c in combs:
        for t in c:
            print (''.join(t), end =' ')
 
# Testing with driver code
if __name__ == '__main__':
    Sub_Sequences('abc')

输出：

a b c ab ac bc abc