标签：open 题意 面试官 取反 ges indicator sed image function
leetcode 191. Number of 1 Bits
题意：
Write a function that takes an unsigned integer and returns the number of ’1‘ bits it has (also known as the Hamming weight).
For example, the 32-bit integer ’11‘ has binary representation 00000000000000000000000000001011, so the function should return 3.
解法：
1.普通解法：利用1的移位相与
1 public class Solution { 2 // you need to treat n as an unsigned value 3 public int hammingWeight(int n) { 4 int flag = 1; 5 int count = 0; 6 while (flag != 0) { 7 if ((n & flag) != 0) { 8 count++; 9 } 10 flag = flag << 1; 11 } 12 return count; 13 } 14 }
2.能给面试官打来惊喜的解法，p80 利用减1的性质：减1其实是把最右边的一个1之后的位取反，再与原数字相与就只剩下了前面的位。
1 public class Solution { 2 // you need to treat n as an unsigned value 3 public int hammingWeight(int n) { 4 int count = 0; 5 while (n != 0) { 6 count++; 7 n = n & (n - 1); 8 } 9 return count; 10 } 11 }
标签：open 题意 面试官 取反 ges indicator sed image function
原文地址：http://www.cnblogs.com/fisherinbox/p/6361194.html
