You probably need to make the returned alias to be const as well.
For info, check the (x = y) = z problem...

in sort _demo.cpp
i find a exception error named std::out_of_range when i run the program.
exactlly,there are something wrong in the heap sort which is about std::vector's using.

8-Queen Problem was typed "8-Queue Problem" in README.md.

Backtracking is not present.
Backtracking is an algorithmic-technique for solving problems recursively by trying to build a solution incrementally.

Hello,

first of all, this is a great compilation of non-trivial algorithms ... thank you for putting it together.

secondly, I get this build error for suffix_tree in my environment.
most probably compiler dependent issues.
I will look into it and if i fix it I will send a pull request from a fork.

In file included from src/suffix_tree_demo.cpp:1:0:
./include/suffix_tree.h: In member function ‘Iterator SuffixTree::inc_search(Iterator)’:
./include/suffix_tree.h:34:41: warning: typedef ‘T’ locally defined but not used [-Wunused-local-typedefs]
typedef typename Iterator::value_type T; // extract real type
^
./include/suffix_tree.h: In function ‘std::ostream& operator<<(std::ostream&, SuffixTree::Node&)’:
./include/suffix_tree.h:214:8: error: ‘typedef struct SuffixTree::Edge SuffixTree::Edge’ is private within this context
map<Edge*, bool>::iterator iter;
^~~~
./include/suffix_tree.h:149:22: note: declared private here
typedef struct Edge Edge;
^~~~
./include/suffix_tree.h:215:14: error: ‘typedef struct SuffixTree::Edge SuffixTree::Edge’ is private within this context
map<char, Edge*>::iterator iter_f;
^~~~
./include/suffix_tree.h:149:22: note: declared private here
typedef struct Edge Edge;
^~~~
src/suffix_tree_demo.cpp: At global scope:
src/suffix_tree_demo.cpp:107:70: error: no ‘SuffixTree::Node* SuffixTree::seperate_edge(SuffixTree::Node_, SuffixTree::Edge_)’ member function declared in class ‘SuffixTree’
SuffixTree::Node* SuffixTree::seperate_edge(Node * node, Edge* a_edge)
^
src/suffix_tree_demo.cpp:107:13: error: ‘typedef struct SuffixTree::Node SuffixTree::Node’ is private within this context
SuffixTree::Node* SuffixTree::seperate_edge(Node * node, Edge* a_edge)
^~~~
In file included from src/suffix_tree_demo.cpp:1:0:
./include/suffix_tree.h:81:22: note: declared private here
typedef struct Node Node;
^~~~
src/suffix_tree_demo.cpp:107:58: error: ‘typedef struct SuffixTree::Edge SuffixTree::Edge’ is private within this context
SuffixTree::Node* SuffixTree::seperate_edge(Node * node, Edge* a_edge)
^~~~
In file included from src/suffix_tree_demo.cpp:1:0:
./include/suffix_tree.h:149:22: note: declared private here
typedef struct Edge Edge;
^~~~
Makefile:257: recipe for target 'suffix_tree_demo' failed
make: *** [suffix_tree_demo] Error 1

hi，各位：
我的代码环境：g++ 4.8.4, Ubuntu 14.04.6，kernel 4.4.0-148-generic
失败的地方是在 src/double_linked_list_demo.cpp 中的代码：

	list_for_each_prev(pos, &head){
		struct DemoNode * node = list_entry(pos, struct DemoNode, list);
		printf("%d\n", node->key);
	}
	
	list_for_each_entry(node, &head, list){
		printf("%d\n", node->key);
	}

上面demo 示例，list_for_each_prev 中，list_entry中的type 参数是struct DemoNode， 但在 list_for_each_entry 中使用 typeof(*pos) (也就是decltype(*pos) ) ， 它返回的type 为 struct DemoNode& ， 也就导致编译失败。我做了下面的简单修复.

其中原来的 list_for_each_entry 的实现

#ifndef _MSC_VER
#define list_for_each_entry(pos, head, member)				\
	for (pos = list_entry((head)->next, typeof(*pos), member);	\
	     &pos->member != (head); 					\
	     pos = list_entry(pos->member.next, typeof(*pos), member))
#else
#define list_for_each_entry(pos, head, member)				\
	for (pos = list_entry((head)->next, typeof(pos), member);	\
	     &pos->member != (head); 					\
	     pos = list_entry(pos->member.next, typeof(pos), member))
#endif

修复：

#define list_for_each_entry(pos, head, member)               \
  for (pos = list_entry_ptr((head)->next, typeof(pos), member); \
       &pos->member != (head);                               \
       pos = list_entry_ptr(pos->member.next, typeof(pos), member))

#define list_entry_ptr(ptr, ptrtype, member) \
  (reinterpret_cast<ptrtype>(            \
      (char *)(ptr) - (char *)(&(reinterpret_cast<ptrtype>(1)->member)) + 1))

Hey man, while using your fantastic rep I encountered a bug in the astar header, in particular the indexing of the grid in the neighbor search when using nx,ny and cx,cy where swapped. That was causing the algorithm to search blocks that could be occupied by walls if the map was different from the sample one. I'm using your astar header in one of my repositories, so if you want feel free to have a look at the changes I've done 😉

I'm not using the github tools to fork the rep and request a merge since I'm somehow new to git and I don't want to create a mess 👅

Error message is like following.

c++: error: /FImsvc/alg_vs.h: 没有那个文件或目录
CMakeFiles/astar_demo.dir/build.make:62: recipe for target 'CMakeFiles/astar_demo.dir/src/astar_demo.cpp.o' failed
make[3]: *** [CMakeFiles/astar_demo.dir/src/astar_demo.cpp.o] Error 1
CMakeFiles/Makefile2:992: recipe for target 'CMakeFiles/astar_demo.dir/all' failed
make[2]: *** [CMakeFiles/astar_demo.dir/all] Error 2
CMakeFiles/Makefile2:1004: recipe for target 'CMakeFiles/astar_demo.dir/rule' failed
make[1]: *** [CMakeFiles/astar_demo.dir/rule] Error 2
Makefile:443: recipe for target 'astar_demo' failed
make: *** [astar_demo] Error 2

Having looked through the CmakeList.txt, it seams that the default msvc building option is not open.
So how to build on Ubuntu/Linux?
I am new to Cmake, could you tell me how to fix this?

After looking at this project i want to say that this project is good for the one who is learning algorithm. The only opinion i could give right now is that if possible we could segregate the implementations in include directory( only contains the declarations ) and move it to .cpp file( some src directory). It not only helps in readability of the code but also the compile time could increase.

memset(update, 0, SL_MAX_LEVEL + 1);
error size isn't it ?

and make_node use 0 to build a value that may not init with arg 0

Hi,
this is an awesome repository which contains a lot of useful algorithms for C++, but the code style, I think, could be improved:

• Use <cstddef> instead of <stddef.h>
• each identifier with two underscores at the beginning(__foobar) or one underscore followed by character in uppercase(_Foobar) is reserved by language
• the void keyword could be omitted inint main(void), so is struct in struct Foo obj

include<stdio.h>

include<stdlib.h>

int ch,i,item,f=0,r=0,q[5],max=5,c=0;
void insert();
void Delete();
void display();
void main()
{
for(;;)
{
printf("\n\tMENU\n1.INSERT\n2.DELETE\n3.DISPLAY\n4.EXIT\n");
printf("Enter your Choice\n");
scanf("%d", &ch);
switch(ch)
{
case 1: insert();
display();
break;
case 2: Delete();
display();
break;
case 3: display();
break;
case 4: exit(0);

         default: printf("Invalid Input\n");
    }
}

}
void insert()
{
if(f==r && c==max)
{
printf("Insertion not possible, due to overflow\n");
}
else
{
printf("Enter the element to be inserted\n");
scanf("%d", &item);
q[r]=item;
r=(r+1)%max;
c++;
}
}
void Delete()
{
if(f==r && c==0)
{
printf("Deletion is not possible, due to underflow\n");
}
else
{
printf("The item deleted is %d\n",q[f]);
f=(f+1)%max;
c--;
}
}
void display()
{
printf("The circular queue is \n");
for(i=f;i<c+f;i++)
{
printf("%d",q[i]);

 }

}

In https://github.com/xtaci/algorithms/blob/master/include/quick_sort.h

在目前（2013年10月21日 16时12分55秒）快速排序算法的实现中，枢纽值pivot是通过随机数选取的，即int pivot_idx = RANDOM(begin,end);但这不是最高效的枢纽选择策略。
对快速排序效率影响最大的是枢纽值pivot的选择，建议采取首值、中间值和末尾值进行比较，选择中间大小的那个值作为枢纽值pivot策略。这样在数据量大的情况下，排序效果会更加高效。

可以详见博客描述：http://blog.csdn.net/nwpu_kexie/article/details/7538673

ok, i merge k-means , great job!!!

i think adding more comments for k-means functions will be helpful for successor.

makefile creates many unused files. use *.o to remove those files

https://github.com/Samana

samana added support for msvc... really great work!

thanks...

define RANDOM(L, R) (L + rand() % ((R) - (L))) // gen a random integer in [L, R]

I think the RANDOM cannot get R, it should be (L + rand() % ((R) - (L) + 1))

Hello,
In "queue.h"
We use uint32_t for m_front and m_rear and other member variables.
However in constructor, we are assigning m_rear as -1.
I understand the purpose of assigning it -1, as we want to enqueue first element at m_rear = 0 and we increment m_rear with each enqueue operation.
Although, the code behaves right, as assigning -1 would overflow it to UMAX and then adding 1 to it will bring it back to 0. I just wanted to understand the purpose of declaring it uint32_t instead of simple integer.

Your repository is really awesome, learning a lot from it.

Thanks

Hello , I am new to the Github and i have decent knowledge about the data structures and algorithms . How can i start contributing ?

个人觉得链表的头和尾p_cache_list_head, p_cache_list_near
用类似p_cache_list_head, p_cache_list_tail
或者 p_cache_list_front, p_cache_list_rear感觉更好些
p_cache_list_near的意思读起来不是很清晰

That's a terrible question

Look this.
I can't compile kruskal_mst.h.
Who can help me?

Message:
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h: In member function ‘alg::Graph* alg::Kruskal::run()’:
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h:143:41: error: ‘class alg::Heapalg::Graph::Vertex*’ has no member named ‘min_key’
if(!pa->heap.is_empty()&&pa->heap.min_key()<weight) {
^~~~~~~
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h:144:26: error: ‘class alg::Heapalg::Graph::Vertex*’ has no member named ‘min_key’
weight = pa->heap.min_key();
^~~~~~~
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h:145:21: error: ‘class alg::Heapalg::Graph::Vertex*’ has no member named ‘min_value’
v = pa->heap.min_value();
^~~~~~~~~
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h:174:23: error: ‘class alg::Heapalg::Graph::Vertex*’ has no member named ‘delete_min’
best_from->heap.delete_min();
^~~~~~~~~~
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h:175:29: error: ‘class alg::Heapalg::Graph::Vertex*’ has no member named ‘delete_min’
lookup(best_to)->heap.delete_min();
^~~~~~~~~~
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h: In member function ‘void alg::Kruskal::print()’:
/home/yangjz/code/forkprojects/algorithms/include/kruskal_mst.h:191:35: error: no match for ‘operator[]’ (operand types are ‘alg::Heapalg::Graph::Vertex*’ and ‘uint32_t {aka unsigned int}’)
Graph::Vertex * v = pa->heap[i];

Hi, I found this repo interesting to contribute with some of my data structures and C++ implementations of algorithms, but I can only build the demos using the UNIX makefile. For some reason, the cmake project
setup is broken and it fails after running the Makefile generated by cmake.

I think it's because the include folders are not set accordingly. I'll try to fix it myself before adding my code. If I succeed, I'll send you my pull request. Thanks for the great work!