[LeetCode] Single Number II

Single Number II

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?

比较坑的是提交几次发现 符号位老是丢掉，不明所以，后来发现是

const int MASK 这行出现了问题， 应该是 const unsigned int MASK，然后就好了。

class Solution {
public:
int singleNumber(int A[], int n) {
// Note: The Solution object is instantiated only once and is reused by each test case.
assert(A&&n>0&&(n-1)%3==0);
unsigned int ans=0;
for(int i=0;i<32;i++)
{
const unsigned int MASK=(1<<i);
int t=0;
for(int j=0;j<n;j++)
t+=(A[j]&MASK)>0?1:0;
ans|=(t%3==0)?0:MASK;
}
return (int)ans;
}
};