Find First Non-Repeating Number in Integer Array using Java

To find the first non-repeating number in an array −

• Construct count array to store count of each element in the given array with same length and with initial value 0 for all elements.
• Compare each element in the array with all other elements, except itself.
• If match occurs increment its value in the count array.
• Get the index of the first 0 in the count array and print the element in the input array at this index.

Example

import java.util.Arrays;
public class NonRpeatingArray {
   public static void main(String args[]) {
      int array[] = {114, 225, 669, 996, 336, 6547, 669, 225, 336, 669, 996, 669, 225 };
      System.out.println("");
      //Creating the count array
      int countArray[] = new int[array.length];
      for(int i=0; i<array.length; i++) {
         countArray[i] = 0;
      }
      for(int i=0; i<array.length; i++) {
         for(int j=0; j<array.length;j++) {
            if(i!=j && array[i]==array[j]) {
               countArray[i]++;
            }
         }
      }
      System.out.println(Arrays.toString(countArray));
      //First non-repeating element in the array
      for(int i=0; i<array.length; i++) {
         if(countArray[i]==0) {
            System.out.println(array[i]);
            break;
         }
      }
   }
}

Output

[0, 2, 3, 1, 1, 0, 3, 2, 1, 3, 1, 3, 2]
114