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Interview Classic 150 Questions P136 Single Number

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2025-11-25

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Bit Manipulation

Problem:

P136 Single Number

https://leetcode.cn/problems/single-number/description/?envType=study-plan-v2&envId=top-interview-150

Mainly uses XOR operation: same bits clear to 0, different bits set to 1.

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#include <vector>
using std::vector;

class Solution {
    public:
	int singleNumber(vector<int> &nums)
	{
		int i, n = nums.size();

		int res = nums[0];
		for (i = 1; i < n; i++) {
			res = res ^ nums[i];
		}
		return res;
	}
};

leetcode hot 100 rewrite

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#include <vector>
using std::vector;

class Solution {
    public:
        int singleNumber(vector<int> &nums)
        {
                int i, n = nums.size();
                int target = nums[0];

                for (i = 1; i < n; i++)
                        target ^= nums[i]; // XOR

                return target;
        }
};