Number of 1 bits

Brute force solution:
Iterate 32 times, each time determining if the ith bit is a ’1′ or not. This is probably the easiest solution, and the interviewer would probably not be too happy about it. This solution is also machine dependent (You need to be sure that an unsigned integer is 32-bit). In addition, this solution is not very efficient too, as you need to iterate 32 times no matter what.

    static int countSetBits(long n){int count = 0;while(n!=0){count += n & 1;n >>= 1;}return count;}

Best solution:
Hint: Remember my last post about making use x & (x-1) to determine if an integer is a power of two? Well, there are even better uses for that! Remember every time you perform the operation x & (x-1), a single 1 bit is erased?

The following solution is machine independent, and is quite efficient. It runs in the order of the number of 1s. In the worst case, it needs to iterate 32 times (for a 32-bit integer), but a case such as the number ’8′ would only need to iterate 1 time.

int number_of_ones(unsigned int x) {int total_ones = 0;while (x != 0) {x = x & (x-1);total_ones++;}return total_ones;
}

转载于:https://www.cnblogs.com/leetcode/p/4020088.html

Number of 1 bits相关推荐

LeetCode 191 Number of 1 Bits
LeetCode 191 Number of 1 Bits 解法一(较为传统都解法):使用将n不断右移,并与1想&得到1的个数:(也有使用除法/2的,明显除法的运行效率要低于位移) 时间复杂度 ...
领扣-191 位1的个数 Number of 1 Bits MD
Markdown版本笔记我的GitHub首页我的博客我的微信我的邮箱 MyAndroidBlogs baiqiantao baiqiantao bqt20094 baiqiantao@sina ...
leetcode 191. Number of 1 Bits
Write a function that takes an unsigned integer and returns the number of '1' bits it has (also know ...
Leetcode PHP题解--D57 762. Prime Number of Set Bits in Binary Representation
2019独角兽企业重金招聘Python工程师标准>>> D57 762. Prime Number of Set Bits in Binary Representation 题目链接 ...
【LeetCode从零单排】No 191.Number of 1 Bits(考察位运算)
题目 Write a function that takes an unsigned integer and returns the number of '1' bits it has (also k ...
leetcode Number of 1 Bits
题目连接 https://leetcode.com/problems/number-of-1-bits/ Number of 1 Bits Description Write a function t ...
【LeetCode】191. Number of 1 Bits
题目: Write a function that takes an unsigned integer and returns the number of '1' bits it has (also ...
[LeetCode] Number of 1 Bits Reverse Integer - 整数问题系列
目录: 1.Number of 1 Bits - 计算二进制1的个数 [与运算] 2.Contains Duplicate - 是否存在重复数字 [遍历] 3.Reverse Integer - 翻 ...
Leet Code OJ 191. Number of 1 Bits [Difficulty: Easy]
题目: Write a function that takes an unsigned integer and returns the number of '1' bits it has (also ...
LeetCode - Easy - 191. Number of 1 Bits
Topic Bit Manipulation Description https://leetcode.com/problems/number-of-1-bits/ Write a function ...

Number of 1 bits

Number of 1 bits相关推荐

最新文章

热门文章