Given a string, we have to find out all subsequences of it. A String is a subsequence of a given String, that is generated by deleting some character of a given string without changing its order.
Input : abc Output : a, b, c, ab, bc, ac, abc Input : aaa Output : a, aa, aaa
Method 1 (Pick and Don’t Pick Concept)
[abcd, abc, abd, ab, acd, ac, ad, a, bcd, bc, bd, b, cd, c, d, ]
Step 1: Iterate over the entire String Step 2: Iterate from the end of string in order to generate different substring add the subtring to the list Step 3: Drop kth character from the substring obtained from above to generate different subsequence. Step 4: if the subsequence is not in the list then recur.
Below is the implementation of the approach.
[aa, a, ab, bc, ac, b, aac, abc, c, aab, aabc]
Method 3 :
One by one fix characters and recursively generates all subsets starting from them. After every recursive call, we remove last character so that next permutation can be generated.
c ca cab cb a ab b
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