JavaScript: Find the shortest possible string which can create a string to make it a palindrome by adding characters to the end of it

JavaScript Basic: Exercise-97 with Solution

Shortest String to Convert into Palindrome

Write a JavaScript program to find the shortest possible string. This can be converted into a string and converted into a palindrome by adding characters to the end of it.

Sample Solution:

JavaScript Code:

// Function to build a palindrome from a given string
function build_Palindrome(new_str) {
  var flag; // Variable to check if a palindrome is found
  for (var i = new_str.length;; i++) { // Loop to increment the length for building a palindrome
    flag = true; // Set the flag initially to true for each iteration
    for (var j = 0; j < i - j - 1; j++) { // Loop to check for palindrome condition
      // Check if characters symmetrically positioned around the center are equal
      if (i - j - 1 < new_str.length && new_str[j] != new_str[i - j - 1]) {
        flag = false; // Set flag to false if characters are not equal
        break; // Break the loop if not a palindrome
      }	
    }
    if (flag) {
      // If a palindrome is found, complete the palindrome by adding the remaining characters
      for (var j = new_str.length; j < i; j++) {
        new_str += new_str[i - j - 1];
      }
      return new_str; // Return the palindrome
    }
  }
}

console.log(build_Palindrome("abcddc")); // Output the result for the given string
console.log(build_Palindrome("122")); // Output the result for the given string

Output:

abcddcba
1221

Live Demo:

See the Pen javascript-basic-exercise-97 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to build a palindrome from a given string
const build_Palindrome = (new_str) => {
  let flag;  // Variable to check if a palindrome is found
  for (let i = new_str.length;; i++) {  // Infinite loop starting from the length of the input string
    flag = true;  // Reset the flag for each iteration
    for (let j = 0; j < i - j - 1; j++) {
      // Check if the characters symmetrically positioned around the center are equal
      if (i - j - 1 < new_str.length && new_str[j] !== new_str[i - j - 1]) {
        flag = false;  // Set the flag to false if not equal
        break;  // Break the inner loop
      }
    }
    if (flag) {
      // If a palindrome is found, complete the palindrome by adding the remaining characters
      for (let j = new_str.length; j < i; j++) {
        new_str += new_str[i - j - 1];
      }
      return new_str;  // Return the palindrome
    }
  }
}

console.log(build_Palindrome("abcddc"));  // Example usage
console.log(build_Palindrome("122"));  // Example usage

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