Java Program to Find Palindrome Numbers in Given Range

Java program to find palindrome numbers in given range

Your temp is not incrementing by 1 in the loop.

// temp is initialized to start at first
while(temp != 0){
    rem = temp % 10;
    rev = rev * 10 + rem;
    temp = temp / 10;
}
// at the end of this temp's value is entirely changed.
// above temp is incremented here, ideally temp at the start should be incremented. You can do this by initializing temp as i
temp++;

search palindrome number in a list of array. if there exist palindrome number in the list, return its size

Here is a pseudo code.

output = -1;
for (i = 0; i < list.length; i++){
    num = list[i];
    indices[] = \\ get all the indices which the "num" value appears, only include those indices that are greater than "i"
    for (j = 0; j < indices.length; j++){
        flag = true;
        k = i;
        for (l = indices[j]; l >= k; l--, k++){
             if (list[k] != list[l]) {
                 flag = false;
                 break;
             } 
        }
        if (flag){
           length = (indices[j] - i) + 1;
           if (length != 1 && length > output) { // checking of length != 1 will exclude those palindromes of length 2
               output = length;
           }
        }
    }
}
return output;

Here is the full code.

public class Main {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int[] list = { 3, 5, 2, 2, 6, 3, 6, 3, 6, 3, 6, 2, 2, 1 };
        System.out.print(palindrome(list));
    }

    public static int palindrome(int[] list) {
        int output = -1;
        for (int i = 0; i < list.length; i++) {
            int num = list[i];
            ArrayList<Integer> indices = getIndices(list, i, num);
            for (int j = 0; j < indices.size(); j++) {
                boolean flag = true;
                int k = i;
                for (int l = indices.get(j); l >= k; l--, k++) {
                    if (list[k] != list[l]) {
                        flag = false;
                        break;
                    }
                }
                if (flag) {
                    int length = (indices.get(j) - i) + 1;
                    if (length != 1 && length > output) {
                        output = length;
                    }
                }
            }
        }
        return output;
    }

    public static ArrayList<Integer> getIndices(int[] list, int start, int num) {
        ArrayList<Integer> result = new ArrayList<Integer>();

        for (int i = start + 1; i < list.length; i++) {
            if (list[i] == num) {
                result.add(i);
            }
        }

        return result;
    }

}

Palindrome Number

A little modified and tested code is here,

public boolean isPalindrome(int x)
   {

      int reverse = 0;
      int remainder = 0;
      int originalX = x;

      while (x > 0)
      {
         remainder = x % 10;
         reverse = reverse * 10 + remainder;
         x = x / 10;
      }

      return (reverse == originalX);

   }

Trying to find palindrome number

Because after your while loop ends, x will be 0, you have to act on a copy instead

   public boolean isPalindrome(int x) {
        int num = x;
        if(x<0 || x%10==0){
            return false;
        }
        int rev = 0;
        while(x!=0){
            rev=(rev*10)+(x%10);
            x/=10;
        }
        
        if(num==rev){
            return true;
        }
        else{
            return false;
        }
    }

---

Related Topics