LeetCode75-136-Single-Number

🧠 Summary of Thoughts

Use the bitwise XOR (^) operation to cancel out duplicate numbers.

XOR has two important properties:

• a ^ a = 0 → same numbers cancel out
• a ^ 0 = a → zero does not affect the result

Every number that appears twice cancels itself out. The only number left is the one that appears once. We can also reorder the ^’s left and right number to cancel the duplicate out :)

✅ Code（Java）

class Solution {
    public int singleNumber(int[] nums) {
        int ans = 0;
        for (int num : nums) {
            ans ^= num;
        }
        return ans;
    }
}