Check if given Morse Code is valid

Given a string S representing a Morse Code, the task is to check is the code is valid or not. A Morse code is valid if that meets all the below requirements:

• Any message must begin with a dot. [ ‘.’ ]
• Any message must end with a dash. [ ‘-‘ ]
• Every dot must have a corresponding dash after it to close it.

Examples:

Input: S = “.–“
Output: Valid

Input: S = “.”
Output: Invalid

Input: S = “-“
Output: Invalid

Approach: This is a simple implementation based problem where the first, last and each pair of characters need to be checked for the given conditions. Follow the given steps to solve the problem:

• If the first or last characters are not dot and dash respectively then the string is invalid.
• Traverse the message from 0 to N-1:
  • If the character at index i is a dot but at index i+1 is not a dash (-), then the code is invalid.
• If the loop ends, means the message has met all the requirements. So the code is valid.

Below is the implementation for the above approach:

C++14

// C++ code to implement the approach

#include <bits/stdc++.h>
using namespace std;

// Function to find if
// the Morse code is valid or not
bool isValidMorse(string& code)
{
    int n = code.length();

    if (code[0] != '.' || code[n - 1] != '-')
        return 0;

    for (int i = 0; i < n - 1; i++) {
        if (code[i] == '.' && code[i + 1] != '-')
            return 0;
    }

    return 1;
}

// Driver's code
int main()
{
    string code = ".--";

    // Function Call
    if (isValidMorse(code))
        cout << "Valid";
    else
        cout << "Invalid";
    return 0;
}

Java

/*package whatever //do not write package name here */
import java.io.*;

class GFG {
  // Java code to implement the approach

  // Function to find if
  // the Morse code is valid or not
  static boolean isValidMorse(String code)
  {
    int n = code.length();

    if (code.charAt(0) != '.' || code.charAt(n - 1) != '-')
      return false;

    for (int i = 0; i < n - 1; i++) {
      if (code.charAt(i) == '.' && code.charAt(i + 1) != '-')
        return false;
    }

    return true;
  }


  /* Driver program to test above function*/
  public static void main(String args[])
  {
    String code = ".--";

    // Function Call
    if (isValidMorse(code))
      System.out.println("Valid");
    else
      System.out.println("Invalid");
  }
}

// This code is contributed by shinjanpatra.

Python3

# Python3 code to implement the approach

# Function to find if
# the Morse code is valid or not
def isValidMorse(code):

    n = len(code)

    if (code[0] != '.' or code[n - 1] != '-'):
        return 0

    for i in range(n-1):
        if (code[i] == '.' and code[i + 1] != '-'):
            return 0

    return 1

# Driver's code

code = ".--"

# Function Call
if (isValidMorse(code)):
    print("Valid")
else:
    print("Invalid")

# This code is contributed by shinjanpatra

C#

/*package whatever //do not write package name here */
using System;

public class GFG
{

  // C# code to implement the approach

  // Function to find if
  // the Morse code is valid or not
  static bool isValidMorse(String code)
  {
    int n = code.Length;

    if (code[0] != '.' || code[(n - 1)] != '-')
      return false;

    for (int i = 0; i < n - 1; i++) {
      if (code[i] == '.' && code[(i + 1)] != '-')
        return false;
    }

    return true;
  }


  /* Driver program to test above function*/
  public static void Main(String []args)
  {
    String code = ".--";

    // Function Call
    if (isValidMorse(code))
      Console.WriteLine("Valid");
    else
      Console.WriteLine("Invalid");
  }
}

// This code contributed by shikhasingrajput

Javascript

<script>
       // JavaScript code for the above approach


       // Function to find if
       // the Morse code is valid or not
       function isValidMorse(code) {
           let n = code.length;

           if (code[0] != '.' || code[n - 1] != '-')
               return 0;

           for (let i = 0; i < n - 1; i++) {
               if (code[i] == '.' && code[i + 1] != '-')
                   return 0;
           }

           return 1;
       }

       // Driver's code

       let code = ".--";

       // Function Call
       if (isValidMorse(code))
           document.write("Valid");
       else
           document.write("Invalid");

   // This code is contributed by Potta Lokesh
   </script>

Output

Valid

Time Complexity: O(N)
Auxiliary Space: O(1)