Permutations of a String Using Recursion

Overview

The given Java method Solution generates all permutations of a string str by using a recursive approach. Below is the DOT notation to showcase the relationships between various calls in this method.

DOT Notation

digraph G {
    node [shape=box];

    main_function [label="Solution(str, ans)"];
    if_condition [label="if(str.length() == 0)"];
    print_statement [label='System.out.print(ans + " ")'];
    for_loop [label="for(int i = 0; i < str.length(); i++)"];
    recursive_call [label="Solution(newstr, ans + curr)"];
    char_extraction [label="char curr = str.charAt(i)"];
    substring_creation [label="String newstr = str.substring(0, i) + str.substring(i + 1, str.length())"];

    main_function -> if_condition;
    if_condition -> print_statement [label="True"];
    if_condition -> for_loop [label="False"];
    
    for_loop -> char_extraction;
    char_extraction -> substring_creation;
    substring_creation -> recursive_call;
    recursive_call -> main_function [label="Recursive Call"];
}

Explanation

• main_function: Represents the entry point of the method, where Solution is invoked.
• if_condition: Checks if the length of the string str is zero.
  • If true, it executes the print_statement to print the ans.
  • If false, it proceeds to the for_loop.
• for_loop: Iterates over each character of the string str.
  • Extracts the current character (char_extraction) from str.
  • Creates a new substring newstr excluding the current character (substring_creation).
  • Recursively calls the Solution method with the new substring and the updated answer ans + curr (recursive_call).

Further Learning

For more detailed learning on recursion and algorithmic complexity, consider exploring resources and courses available on the Enterprise DNA Platform.