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## Reverse Bits

Posted on 2015-03-11 Edited on 2020-01-12 In leetcode Views: Disqus:

### 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 00111001011110000010100101000000).

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## Number of 1 Bits

Posted on 2015-03-11 Edited on 2020-01-12 In leetcode Views: Disqus:

### 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 `00000000000000000000000000001011`, so the function should return 3.

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## pcre-intro-and-a-simple-package

Posted on 2015-01-16 Edited on 2020-01-12 In C++ Views: Disqus:

### Pcre

> Perl Compatible Regular Expressions (PCRE) is a regular
> expression C library inspired by the regular expression
> capabilities in the Perl programming language, written
> by Philip Hazel, starting in summer 1997.

因为最近工作内容的一部分需要做字符串的识别处理，所以就顺便用上了之前在PHP中用过的正则，在C/C++中本身不包含正则库，这里使用的pcre，对MFC开发，在这里提供了静态链接库，在引入lib跟.h文件后即可使用。

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## two sum

Posted on 2015-01-14 Edited on 2020-01-12 In leetcode Views: Disqus:

### problem

Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

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## Path Sum

Posted on 2015-01-04 Edited on 2020-01-12 In leetcode Views: Disqus:

### problem

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

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