Given a string str of length N, the task is to print all possible non-empty subsequences of the given string such that the subsequences either contains characters or ASCII value of the characters from the given string.
Examples:
Input: str = “ab”
Output: b 98 a ab a98 97 97b 9798
Explanation:
Possible subsequence of the strings are { b, a, ab }.
Possible subsequences of the string generated by including either the characters or the ASCII value of the characters from the given string are { 98, b, a, 97, ab, 97b, a98, 9798 }.
Therefore, the required output is { b, 98, a, ab, a98, 97, 97b, 9798 }.Input: str = “a”
Output: a 97
Approach: Follow the steps below to solve the problem:
- Iterate over each character of the given string using variable i to generate all possible subsequences of the string.
- For every ith character, the following three operations can be performed:
- Include the ith character of str in a subsequence.
- Do not include the ith character of str in a subsequence.
- Include the ASCII value of ith character of str in a subsequence.
- Therefore, the recurrence relation to solve this problem is as follows:
FindSub(str, res, i) = { FindSub(str, res, i + 1), FindSub(str, res + str[i], i + 1), FindSub(str, res + ASCII(str[i]), i + 1) }
res = subsequence of the string
i = index of a character in str
- Using the above recurrence relation, print all possible subsequences based on the given conditions.
Below is the implementation of the above approach:
C++
// C++ program to implement// the above approach#include<bits/stdc++.h>using namespace std;// Function to print subsequences containing// ASCII value of the characters or the// the characters of the given stringvoid FindSub(string str, string res, int i){ // Base Case if (i == str.length()) { // If length of the // subsequence exceeds 0 if (res.length() > 0) { // Print the subsequence cout << res << " "; } return; } // Stores character present at // i-th index of str char ch = str[i]; // If the i-th character is not // included in the subsequence FindSub(str, res, i + 1); // Including the i-th character // in the subsequence FindSub(str, res + ch, i + 1); // Include the ASCII value of the // ith character in the subsequence FindSub(str, res + to_string(int(ch)), i + 1);}// Driver Codeint main(){ string str = "ab"; string res = ""; // Stores length of str int N = str.length(); FindSub(str, res, 0);}// This code is contributed by ipg2016107 |
Java
// Java program to implement// the above approachclass GFG { // Function to print subsequences containing // ASCII value of the characters or the // the characters of the given string static void FindSub(String str, String res, int i) { // Base Case if (i == str.length()) { // If length of the // subsequence exceeds 0 if (res.length() > 0) { // Print the subsequence System.out.print(res + " "); } return; } // Stores character present at // i-th index of str char ch = str.charAt(i); // If the i-th character is not // included in the subsequence FindSub(str, res, i + 1); // Including the i-th character // in the subsequence FindSub(str, res + ch, i + 1); // Include the ASCII value of the // ith character in the subsequence FindSub(str, res + (int)ch, i + 1); ; } // Driver Code public static void main(String[] args) { String str = "ab"; String res = ""; // Stores length of str int N = str.length(); FindSub(str, res, 0); }} |
Python3
# Python3 program to implement# the above approach# Function to print subsequences containing# ASCII value of the characters or the# the characters of the given stringdef FindSub(string , res, i) : # Base Case if (i == len(string)): # If length of the # subsequence exceeds 0 if (len(res) > 0) : # Print the subsequence print(res, end=" "); return; # Stores character present at # i-th index of str ch = string[i]; # If the i-th character is not # included in the subsequence FindSub(string, res, i + 1); # Including the i-th character # in the subsequence FindSub(string, res + ch, i + 1); # Include the ASCII value of the # ith character in the subsequence FindSub(string, res + str(ord(ch)), i + 1);# Driver Codeif __name__ == "__main__" : string = "ab"; res = ""; # Stores length of str N = len(string); FindSub(string, res, 0); # This code is contributed by AnkitRai01 |
C#
// C# program to implement// the above approachusing System;class GFG{// Function to print subsequences containing// ASCII value of the characters or the// the characters of the given stringstatic void FindSub(string str, string res, int i){ // Base Case if (i == str.Length) { // If length of the // subsequence exceeds 0 if (res.Length > 0) { // Print the subsequence Console.Write(res + " "); } return; } // Stores character present at // i-th index of str char ch = str[i]; // If the i-th character is not // included in the subsequence FindSub(str, res, i + 1); // Including the i-th character // in the subsequence FindSub(str, res + ch, i + 1); // Include the ASCII value of the // ith character in the subsequence FindSub(str, res + (int)ch, i + 1);}// Driver Codepublic static void Main(String[] args){ string str = "ab"; string res = ""; // Stores length of str int N = str.Length; FindSub(str, res, 0);}}// This code is contributed by AnkitRai01 |
Javascript
<script>// JavaScript program to implement// the above approach// Function to print subsequences containing// ASCII value of the characters or the// the characters of the given stringfunction FindSub(str, res, i) { // Base Case if (i === str.length) { // If length of the // subsequence exceeds 0 if (res.length > 0) { // Print the subsequence document.write(res + " "); } return; } // Stores character present at // i-th index of str var ch = str[i]; // If the i-th character is not // included in the subsequence FindSub(str, res, i + 1); // Including the i-th character // in the subsequence FindSub(str, res + ch, i + 1); // Include the ASCII value of the // ith character in the subsequence FindSub(str, res + ch.charCodeAt(0), i + 1);}// Driver Codevar str = "ab";var res = "";// Stores length of strvar N = str.length;FindSub(str, res, 0);// This code is contributed by rdtank</script> |
Output:
b 98 a ab a98 97 97b 9798
Time Complexity: O(3N)
Auxiliary Space: O(N)
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