137. Single number II (Bit)

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

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

Ideas:

STEP1: From single number we know that through easy or operation can be stored in an int for a few times

STEP2: We can get the number of double-digit occurrences by doing with the singular.

STEP3: Try to get rid of the STEP1 int three times.

classSolution { Public:    intSinglenumber (intA[],intN) {intonce =0; inttwice =0;  for(inti =0; I < n; i++) {twice|= once & A[i];//The num appeared 2 timesOnce ^= a[i];//The num appeared 1 times            intNot_three = ~ (once & twice);//The num not appeared 3 timesOnce = Not_three & once;//Remove num appeared 3 times from oncetwice = Not_three & twice;//Remove num appeared 3 times from twice        }          returnonce; }};

137. Single number II (Bit)