LeetCode136 Single Number

  • Given an array of integers, every element appears twice except for one. Find that single one.
    • Notice:Your algorithm should have a linear runtime complexity. Implement it without using extra memory.
  • Analysis:
    • The problem itself is not hard. However, the additional time and spcace overhead limitation is a bit annoying. I have no clue at the first sight of this probelm,either. I finally solve it by referring to others' solutions, which reminds me that xor operation is the key to the problem.
    • We all know A^A equals to zero, then we can xor all the numbers and the final answer will be the number appeaing just once.
  • Code:
  •  1 class Solution {
 2 public:
 3     int singleNumber(int A[], int n) {
 4         int ans = 0;
 5         for (int i = 0; i < n; i++){
 6             ans ^= A[i];             //xor
 7         }
 8         return ans;
 9     }
10 };

     

  • Actually, the code works well not only for appearing twice, but also appearing even times.
  • In next bolg, I will share you will a more general way to handle this kind of question.

posted on 2015-04-10 17:09  Jasonzhang398  阅读(335)  评论(0)    收藏  举报

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