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Certification: Basic Level Accuracy: 0% Submissions: 0 Points: 5

Write a C program to find the element that appears only once in an array where every other element appears exactly twice. Given a non-empty array of integers, every element appears twice except for one. Find that single element.

Example 1
    
  
  • Input: nums = [2,2,1]
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  • Output: 1
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  • Explanation: 
    
      
      
    • Step 1: Scan through the array [2,2,1]
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    • Step 2: Element 2 appears twice
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    • Step 3: Element 1 appears only once
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    • Step 4: Therefore, the output is 1
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Example 2
    
  
  • Input: nums = [4,1,2,1,2]
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  • Output: 4
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  • Explanation: 
    
      
      
    • Step 1: Scan through the array [4,1,2,1,2]
      • 
      
    • Step 2: Element 1 appears twice
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    • Step 3: Element 2 appears twice
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    • Step 4: Element 4 appears only once
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    • Step 5: Therefore, the output is 4
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Constraints
    
  
  • The array will have a length between 1 and 3 × 10^4
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  • Each element in the array will be between -3 × 10^4 and 3 × 10^4
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  • Each element appears exactly twice except for one element which appears only once
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  • Time Complexity: O(n) where n is the length of the array
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  • Space Complexity: O(1)
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Hint
Solution

Solution Hints

    
  
  • A brute force approach would be to count occurrences of each element, but that would require O(n) space
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  • Consider using bitwise operations to solve this problem in O(1) space
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  • XOR (exclusive OR) of a number with itself results in 0
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  • XOR of a number with 0 results in the number itself
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  • XOR has the associative property: (a ^ b) ^ c = a ^ (b ^ c)
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Steps to solve by this approach:

 Step 1: Initialize a variable 'result' to 0.

 Step 2: Iterate through the array elements one by one.

 Step 3: For each element, perform XOR operation with the 'result' variable.

 Step 4: When we XOR a number with itself, it becomes 0.

 Step 5: When we XOR a number with 0, it remains the same.

 Step 6: Due to these properties, duplicate elements will cancel each other out.

 Step 7: The final value of 'result' will be the element that appears only once.

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