Create Power Set: Print all the possible subsequences of the String

Power Set: Print all the possible subsequences of the String

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+Problem Statement: Given a string, find all the possible subsequences of the string.
+
+APPROACH 1
+
+#include<bits/stdc++.h>
+using namespace std;
+vector<string> AllPossibleStrings(string s) {
+	int n = s.length();
+	vector<string>ans;
+	for (int num = 0; num < (1 << n); num++) {
+		string sub = "";
+		for (int i = 0; i < n; i++) {
+			//check if the ith bit is set or not
+			if (num & (1 << i)) {
+				sub += s[i];
+			}
+		}
+		if (sub.length() > 0) {
+			ans.push_back(sub);
+		}
+	}
+	sort(ans.begin(), ans.end());
+	return ans;
+}
+int main()
+{
+
+
+	string s="abc";
+	vector<string>ans = AllPossibleStrings(s);
+	//printint all the subsequence.
+	cout<<"All possible subsequences are "<<endl;
+	for (auto it : ans) {
+		cout << it << " ";
+	}
+
+}
+Output:
+
+All possible subsequences are
+a ab abc ac b bc c
+
+Time Complexity: O(2^n * n)
+
+Reason: O(2^n) for the outer for loop and O(n) for the inner for loop.
+
+Space Complexity: O(1)
+
+
+APPROACH 2
+#include<bits/stdc++.h>
+using namespace std;
+void solve(int i, string s, string &f) {
+	if (i == s.length()) {
+		cout << f << " ";
+		return;
+	}
+	//picking 
+	f = f + s[i];
+	solve(i + 1, s,  f);
+	//poping out while backtracking
+	f.pop_back();
+	solve(i + 1, s,  f);
+}
+int main() {
+	string s = "abc";
+	string f = "";
+	cout<<"All possible subsequences are: "<<endl;
+	solve(0, s, f);
+}
+Output:
+
+All possible subsequences are:
+abc ab ac a bc b c
+
+Time Complexity: O(2^n)
+
+Space Complexity: O(n), recursion stack.