191. 位1的个数

public class Solution {
  // you need to treat n as an unsigned value
  public int hammingWeight(int n) {
       int ans = 0;
       while(n>0) {
          if((n&1)==1) 
              ans++;
          n>>=1;
       }
      return ans;
  }
}

public class Solution {
  public int hammingWeight(int n) {
       int ans = 0;
       int flag = 1;
       for(int i = 0 ; i< 32 ;i++) {
           if((n&flag)!=0) 
               ans++;
           flag<<=1;
       }
       return ans;
   }
}

public int hammingWeight(int n) {
  int sum = 0;
  while (n != 0) {
      sum++;
      n &= (n - 1);
  }
  return sum;
}