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最新文章列表
大话 Python:python 基础巩固 -- 位运算的奥妙
位运算是直接对内存中的二进制位进行操作,因此,它的运算效率相比一般的数学运算是比较高的。一般情况下,位运算主要分为六种:与运算、或运算、异或运算、取反运算、左移运算、右移运算。
在开始之前,先介绍一下将十进制转换成二进制的方法。为节约篇幅说明后面的内容,此处我们直接使用 python 内置的 bin() 函数将整数转换为二进制。
注意:若操作系统为32位,则二进制根据位数补全32位即可,以下用 ...
Python新手学习基础之运算符——位运算
位运算符
位运算实际上是把数字看作二进制来进行计算,它的运算法则如下:
结合实例,来看下位运算是如何进行的吧:
位运算在实际应用中用途很广泛,比如我们经常听到的子网掩码,它其实就是和IP地址做了按位与运算,还有很多用途会在你实际工作中遇到。
看一段实例代码吧,你觉得结果会是备注写的这样的么?
x = 9 #二进制表达为1001
y = 12 #二进制表达为1100
prin ...
为啥要用位运算代替取模呢
为什么很多开源软件中的源码中,使用位运算代替取模操作,比如:
a%b取模的形式都被替换成了a&(b-1) ,前提条件是:b为2的幂(乘方)。
原因:
位运算实现取模只需5个CPU周期,而取模运算符实现至少需要26个CPU周期(注意,是最少!!!)
原文:http://crazyjvm.iteye.com/blog/1725508
言归正传,大家都知道位 ...
Repeated DNA Sequences
All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DN ...
Maximum Product of Word Lengths
Given a string array words, find the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. You may assume that each word will contain only lower case lette ...
Missing Number
Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.
For example,
Given nums = [0, 1, 3] return 2.
通过位运算,将数组里面的元素与对应的下标进行异或运算,得到一个结果re ...
Single Number III
Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.
For example:
Given nums = ...
Bitwise AND of Numbers Range
Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive.
For example, given the range [5, 7], you should return 4.
给定一个范围,通过位与运算计 ...
Number of 1 Bits
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 00000000000 ...
Reverse Bits
Reverse bits of a given 32 bits unsigned integer.
For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as 001110010111 ...
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 e ...
Single Number
Given an array of integers, every element appears twice except for one. Find that single one.
Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra m ...
Divide Two Integers
Divide two integers without using multiplication, division and mod operator.
If it is overflow, return MAX_INT.
题目要求我们不用乘法,除法还有模运算来完成两个整数的除运算。如果溢出时返回最大值。
题目要求返回一个整型,当除数为Integer.MIN_VALUE,被除数为-1时就会越界 ...
Bit Manipulation总结(二)
这篇文章介绍通过位运算求解子集,反转二进制数,判断是否为2的幂等。
1,Number of 1 Bits
给定一个无符号的整数,输出它包含1的个数。
通过右移,依次与1位与,得到1的个数。 代码如下:
public class Solution {
// you need to treat n as an unsigned value
public int hamming ...
Java二进制.位运算.位移运算
二进制、位运算、位移运算
思考题
1、请看下面的代码段,回答a,b,c,d,e结果是多少?
public static void main(String []args){
int a=1>>2;
int b=-1>>2;
...