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Single Number (easy)

Single Number (easy)

Problem Statement

In a non-empty array of integers, every number appears twice except for one, find that single number.

Example 1:

Input: 1, 4, 2, 1, 3, 2, 3
Output: 4

Example 2:

Input: 7, 9, 7
Output: 9

Try it yourself

Try solving this question here:

class SingleNumber {
  public static int findSingleNumber(int[] arr) {
    // TODO: Write your code here
    return -1;
  }
  public static void main( String args[] ) {
    System.out.println(findSingleNumber(new int[]{1, 4, 2, 1, 3, 2, 3}));
  }
}

Solution

One straight forward solution can be to use a HashMap kind of data structure and iterate through the input:

  • If number is already present in HashMap, remove it.
  • If number is not present in HashMap, add
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