Simple analysis of common algorithms in STL _c language

First, non-mutation algorithm

is a set of template functions that do not break operational data, which is used to process sequential data, element lookup, subsequence Search, statistics, and match. Non-mutation algorithms have very wide applicability and can be applied to various containers basically.

1 Finding container element find

It is used to find elements that are equal to a value. It looks for an element equal to value on the iterator interval [first,last) (closed interval), returns the iterator I if the element referred to by the iterator I satisfies *i=value, and fails to find the element that satisfies the condition. Function prototype: Find (V1.begin (), V1.end (), num_to_find);

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

int num_to_find = 6;

Vector<int> v1;

for (int i = 0; i < i++)

V1.push_back (2*i);

Vector<int>::iterator result;

result = Find (V1.begin (), V1.end (), num_to_find);

if (result = = V1.end ())

cout << "no element match found" << num_to_find << Endl;

Else

cout << "The index value of the matching element is" << result-v1.begin () << Endl;

}

2 Condition Lookup container element find_if

Using predicates that return Boolean values to Judge pred, check every element on the iterator interval [first,last) (closed interval), if iterator I satisfies pred (*i) =true, indicates that the element is found and returns the iteration value I (the first qualifying element found); Return to last position. Function prototype: find_if (V.begin (), V.end (), divby5);

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

BOOL Divby5 (int x)

{

return x%5?0:1;

}

void Main ()

{

Vector<int> V (20);

for (int i=0;i<v.size (); i++)

{

v[i]= (i+1) * (i+3);

cout<<v[i]<< ';

}

cout<<endl;

Vector<int>::iterator ilocation;

Ilocation=find_if (V.begin (), V.end (), divby5);

if (Ilocation!=v.end ())

cout<< "Find the first element to be divisible by 5: The index position of the <<*ilocation<<endl<< element is:" <<ilocation-v.begin () < <endl;

}

3 Count the number of container elements equal to a value

List<int> l;
Count (L.begin (), L.end (), value)

4 Condition Statistics COUNT_IF

Count_if (L.begin (), L.end (), pred). The predicate pred the predicate in the same find_if as the meaning. Examples can refer to Example 2.

5 Sub-sequence search

The search algorithm function searches a sequence for a subsequence that matches another sequence. The parameters are the starting position of a sequence, the end position, and the beginning of another sequence, ending position.

Function prototypes: Search (V1.begin (), V1.end (), V2.begin (), V2.end ());

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v1;

cout<< "v1:";

for (int i=0;i<5;i++)

{

V1.push_back (i+5);

Note: The V1 definition does not have a given size, so it is not possible to use an assignment statement directly.

cout<<v1[i]<< ';

}

cout<<endl;

Vector<int> v2;

cout<< "V2:";

for (i=0;i<2;i++)

{

V2.push_back (I+7);

cout<<v2[i]<< ';

}

cout<<endl;

Vector<int>::iterator ilocation;

Ilocation=search (V1.begin (), V1.end (), V2.begin (), V2.end ());

if (Ilocation!=v1.end ())

cout<< "V2 elements are contained in v1, the starting element is" << "v1[" <<ilocation-v1.begin () << '] ' <<endl;

Else

cout<< "V2 elements are not included in V1" <<endl;

}

6 repeat element subsequence search Search_n

Search_n algorithm function Search sequence whether there is a series of element values are a given value of a child sequence. Function prototype: Search_n (V.begin (), V.end (), 3,8), found 3 consecutive elements in V 8

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v;

V.push_back (1);

V.push_back (8);

V.push_back (8);

V.push_back (8);

V.push_back (6);

V.push_back (6);

V.push_back (8);

Vector<int>::iterator i;

I=search_n (V.begin (), V.end (), 3,8);

if (I!=v.end ())

cout<< "Find 3 consecutive elements in V 8" <<endl;

Else

cout<< "3 consecutive elements not found in V 8" <<endl;

}

7 Last subsequence Search Find_end

Function prototype Find_end (V1.begin (), V1.end (), V2.begin (), V2.end ()), and locate the sequence required in V1 in the location required in the V2.

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v1;

V1.push_back (-5);

V1.push_back (1);

V1.push_back (2);

V1.push_back (-6);

V1.push_back (-8);

V1.push_back (1);

V1.push_back (2);

V1.push_back (-11);

Vector<int> v2;

V2.push_back (1);

V2.push_back (2);

Vector<int>::iterator i;

I=find_end (V1.begin (), V1.end (), V2.begin (), V2.end ());

if (I!=v1.end ())

cout<< "V1 to find the last matching v2 sequence in" << "v1[" <<i-v1.begin () << "]" <<endl;

}

second, mutation algorithm

is a set of template functions that can modify container element data. Copy (V.begin (), V.end (), L.begin ()), and the elements in V are copied into L.

1 Elements Copy Copy

Copy Code code as follows:

#include <vector>

#include <list>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v;

V.push_back (1);

V.push_back (3);

V.push_back (5);

List<int> l;

L.push_back (2);

L.push_back (4);

L.push_back (6);

L.push_back (8);

L.push_back (10);

Copy (V.begin (), V.end (), L.begin ());

List<int>::iterator i;

For (I=l.begin (); I!=l.end (); i++)

cout<<*i<< ';

cout<<endl;

}

2 element Transform transform change

Function Prototypes: Transform (V.begin (), V.end (), L.begin (), square); replication, but replicated by some scheme.

Copy Code code as follows:

#include <vector>

#include <list>

#include <algorithm>

#include <iostream>

using namespace Std;

int square (int x)

{

return x*x;

}

void Main ()

{

Vector<int> v;

V.push_back (5);

V.push_back (15);

V.push_back (25);

List<int> L (3);

Transform (V.begin (), V.end (), L.begin (), square);

List<int>::iterator i;

For (I=l.begin (); I!=l.end (); i++)

cout<<*i<< ';

cout<<endl;

}

3 replacing replace

The replace algorithm replaces the specified element value with the new value.

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v;

V.push_back (13);

V.push_back (25);

V.push_back (27);

V.push_back (25);

V.push_back (29);

Replace (V.begin (), V.end (), 25,100);

Vector<int>::iterator i;

For (I=v.begin (); I!=v.end (); i++)

cout<<*i<< ';

cout<<endl;

}

Output is 13 100 27 100 29

4 Condition Replacement Replace_if

Function prototype: replace_if (V.begin (), V.end (), odd,100);

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

bool Odd (int x)

{

return x%2;

}

void Main ()

{

Vector<int> v;

for (int i=1;i<10;i++)

V.push_back (i);

Replace_if (V.begin (), V.end (), odd,100);

Vector<int>::iterator ilocation;

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}

5 n times filled Fill_n

Function prototype Fill_n (V.begin (), 5,-1); jumps to the back 5 positions starting from V.begin-1

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> V (10);

Fill_n (V.begin (), 5,-1);

Vector<int>::iterator ilocation;

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}

Output results:-1-1-1-1-1 0 0 0 0 0

6 randomly generated n elements generate

Function prototypes: Generate_n (V.begin (), 5,rand), and randomly fill in the data from the back 5 positions starting at V.begin.

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> V (10);

Generate_n (V.begin (), 5,rand);

Vector<int>::iterator ilocation;

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}

7 Condition Removal remove_if

The return value is equivalent to removing the end () value of the new vector formed after the element that satisfies the condition is removed.

Function prototype: remove_if (V.begin (), V.end (), even);

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

bool even (int x)

{

return x%2?0:1;

}

void Main ()

{

Vector<int> v;

for (int i=1;i<=10;i++)

V.push_back (i);

Vector<int>::iterator Ilocation,result;

cout<< "before removing:";

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

Result=remove_if (V.begin (), V.end (), even);

cout<< "after removal:";

For (Ilocation=v.begin (); ilocation!=result;ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}

8 Eliminate continuous repeating elements unique

Function prototype: Unique (V.begin (), V.end ());

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v;

V.push_back (2);

V.push_back (6);

V.push_back (6);

V.push_back (6);

V.push_back (9);

V.push_back (6);

V.push_back (3);

Vector<int>::iterator Ilocation,result;

Result=unique (V.begin (), V.end ());

For (Ilocation=v.begin (); ilocation!=result;ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}

Output results: 2 6 9 6 3

Third, sorting algorithm

1. Create Heap Make_heap

2, element into the heap push_heap (default insert last Element)

3, elements out of the heap pop_heap (as with Push_heap, pop_heap must be on the heap operation to have meaning)

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v;

V.push_back (5);

V.push_back (6);

V.push_back (4);

V.push_back (8);

V.push_back (2);

V.push_back (3);

V.push_back (7);

V.push_back (1);

V.push_back (9);

Make_heap (V.begin (), V.end ());

V.push_back (20);

Push_heap (V.begin (), V.end ());

Vector<int>::iterator ilocation;

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

Pop_heap (V.begin (), V.end ());

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}

4 heap Sort sort_heap

Use:

Copy Code code as follows:

Make_heap (V.begin (), V.end ());

Sort_heap (V.begin (), V.end ());

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v;

V.push_back (3);

V.push_back (9);

V.push_back (6);

V.push_back (3);

V.push_back (17);

V.push_back (20);

V.push_back (12);

Vector<int>::iterator ilocation;

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

Make_heap (V.begin (), V.end ());

Sort_heap (V.begin (), V.end ());

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}

Output results:

3 9 6 3 17 20 12
3 3 6 9 12 17 20

5 sorting sort

Function prototypes: Sort (V.begin (), V.end ());

Copy Code code as follows:

#include <vector>

#include <algorithm>

#include <iostream>

using namespace Std;

void Main ()

{

Vector<int> v;

V.push_back (2);

V.push_back (8);

V.push_back (-15);

V.push_back (90);

V.push_back (26);

V.push_back (7);

V.push_back (23);

V.push_back (30);

V.push_back (-27);

V.push_back (39);

V.push_back (55);

Vector<int>::iterator ilocation;

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

Sort (V.begin (), V.end ());//Comparison function default

For (Ilocation=v.begin (); Ilocation!=v.end (); ilocation++)

cout<<*ilocation<< ';

cout<<endl;

}