Java: Check whether two strings are interleaving of a specified string

Java String: Exercise-36 with Solution

Write a Java program to check whether two strings interlive of a given string. Assuming that unique characters are present in both strings.

Visual Presentation:

Sample Solution:

Java Code:

// Import necessary Java utilities.
import java.util.*;

// Define a class named Main.
public class Main {
    
    // The main method to start the execution of the program.
    public static void main(String args[]) {
        // Define three strings.
        String str1 = "MNO";
        String str2 = "PQ";
        String str3 = "PMQNO";
        
        // Print the given string and interleaving strings.
        System.out.println("The given string is: " + str3);
        System.out.println("The interleaving strings are " + str1 + " and " + str2);
        
        // Check if the given string is interleaving of str1 and str2, then print the result.
        System.out.println("The given string is interleaving: " + checkInterleaved(str1, str2, str3));
    }
    
    // Method to check if a string is interleaving of two other strings.
    private static boolean checkInterleaved(String str1, String str2, String CheckInString) {
        int i = 0, j = 0, k = 0;
        
        // If the length of concatenated str1 and str2 doesn't match the length of the checked string, return false.
        if (str1.length() + str2.length() != CheckInString.length()) {
            return false;
        }
        
        // Loop through the checked string.
        while (k < CheckInString.length()) {
            // Check if character at index i in str1 matches with character at index k in CheckInString.
            if (i < str1.length() && str1.charAt(i) == CheckInString.charAt(k)) {
                i++;
            }
            // Check if character at index j in str2 matches with character at index k in CheckInString.
            else if (j < str2.length() && str2.charAt(j) == CheckInString.charAt(k)) {
                j++;
            } else {
                return false;
            }
            k++;
        }
        
        // If lengths of str1, str2, and CheckInString don't match, return false.
        if (!(i == str1.length() && j == str2.length() && k == CheckInString.length())) {
            return false;
        }
        
        return true;
    }
}

Sample Output:

The given string is: PMQNO
The interleaving strings are MNO and PQ
The given string is interleaving: true

The given string is: PNQMO
The interleaving strings are MNO and PQ
The given string is interleaving: false

N.B.: In the 2nd case, in interleave string, N comes before M and in original string str1 = MNO (N comes after M) So it is not interleaved.

Flowchart:

Java Code Editor:

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