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Single Number II

题目描述:

Given an array of integers, every element appears three times except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

解题方案:

该题目的一般方法是开辟一个空间为32的数组bitsum[32],然后遍历题目中给定的数组,将数组中每个整数的每一bit位给分出来,加到bitsum的对应位置。最后再遍历bitsum数组,同时求bitsum[i]%3,将结果做移位操作!下面是该题的代码:

 1 class Solution { 2 public: 3     int singleNumber(int A[], int n) { 4         int bitsum[32] = {0}; 5         int result = 0; 6         for (int i = 0; i < n; ++i) { 7             for (int j = 0; j < 32; ++j) { 8                 bitsum[j] += A[i]>>j & 1; 9             }10         }11         for (int i = 0; i < 32; ++i) {12             result |=bitsum[i] % 3 << i;13         }14         return result;15     }16 };

 

Single Number II