C++ core programming: P19- > STL---- common algorithms

This series of articles is the learning notes of dark horse programmer C++ tutorial. The links of the previous series of articles are as follows
C++ core programming: memory model of P1- > program
C++ core programming: P2- > reference
C++ core programming: P3- > function improvement
C++ core programming: P4- > classes and objects - encapsulation
C++ core programming: P5- > classes and objects - initialization and cleaning of objects
C++ core programming: P6- > classes and objects - c++ object model and this pointer
C++ core programming: P7- > classes and objects - friends
C++ core programming: P8- > classes and objects - operator overloading
C++ core programming: P9- > classes and objects - inheritance
C++ core programming: P10- > classes and objects - polymorphism
C++ core programming: P11- > file operation
C++ core programming: P12- > template ---- function template
C++ core programming: P13- > template ---- class template
C++ core programming: P14- > STL----STL novice
C++ core programming: P15- > STL---- common containers (Part 1)
C++ core programming: P16- > STL---- common containers (Part 2)
C++ core programming: P17- > STL---- function object
C++ core programming: P18- > STL---- common algorithms (Part 1)

1, Common copy and replace algorithms

Learning objectives: master common copy and replacement algorithms
Algorithm Introduction:
Copy / / copy the elements of the specified range in the container to another container
replace / / modify the old element of the specified range in the container to a new element
replace_if / / replace the elements that meet the conditions in the specified range in the container with new elements
Swap / / swap the elements of the two containers


1.1 copy

Function Description: copy the elements in the specified range in the container to another container
Function prototype: copy(iterator beg, iterator end, iterator dest);
Find the element by value, find the iterator that returns the specified position, and the iterator that returns the end cannot be found
beg: start iterator
End: end iterator
dest: target start iterator


Case: test the function of copy

#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;

class myPrints
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	for (int i = 0; i < 10; i++) {
		v1.push_back(i + 1);
	}
	vector<int> v2;
	v2.resize(v1.size());
	copy(v1.begin(), v1.end(), v2.begin());

	for_each(v2.begin(), v2.end(), myPrints());
	cout << endl;
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


1.2 replace

Function Description: modify the old element of the specified range in the container to a new element
Function prototype: replace(iterator beg, iterator end, oldvalue, newvalue);
Replace the old element in the interval with a new element
beg start iterator
End end iterator
oldvalue old element
newvalue new element


Case: test the function of copy

#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v;
	v.push_back(10);
	v.push_back(20);
	v.push_back(50);
	v.push_back(20);
	v.push_back(40);
	v.push_back(70);

	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
	replace(v.begin(), v.end(), 20, 2000);
	for_each(v.begin(), v.end(), myPrint());
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


1.3 replace_if

Function Description: replace the elements that meet the conditions in the interval with the specified elements
Function prototype: replace_if(iterator beg, iterator end, _pred, newvalue);
Replace the elements according to the conditions, and replace the elements that meet the conditions with the specified elements
beg: start iterator
End: end iterator
_ pred: predicate
newvalue: replaced new element


Case: Test replace_ Functions of if

#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

class Greater30
{
public:
	bool operator()(int val)
	{
		return val >= 30;
	}
};

void test01()
{
	vector<int> v;
	v.push_back(10);
	v.push_back(20);
	v.push_back(50);
	v.push_back(20);
	v.push_back(40);
	v.push_back(70);

	//Replace those greater than or equal to 30 with 3000
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
	replace_if(v.begin(), v.end(), Greater30(), 3000);
	for_each(v.begin(), v.end(), myPrint());
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


1.4 swap

Function Description: exchange elements of two containers
Function prototype: swap(container c1, container c2);
Swap elements of two containers
c1: container 1
c2: container 2


Case: test the function of swap

#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++) {
		v1.push_back(i);
		v2.push_back(i + 100);
	}

	cout << "Before exchange: " << endl;
	for_each(v1.begin(), v1.end(), myPrint());
	cout << endl;
	for_each(v2.begin(), v2.end(), myPrint());
	cout << endl;

	cout << "After exchange: " << endl;
	swap(v1, v2);
	for_each(v1.begin(), v1.end(), myPrint());
	cout << endl;
	for_each(v2.begin(), v2.end(), myPrint());
	cout << endl;
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


2, Common arithmetic generation algorithm

Learning objectives: master common arithmetic generation algorithms
Note: the arithmetic generation algorithm is a small algorithm, and the header file included when using is \include <numeric>
Algorithm Introduction:
accumulate / / calculate the cumulative sum of container elements
fill / / add elements to the container


2.1 accumulate

Function Description: calculate the cumulative sum of interval content elements
Function prototype: accumulate(iterator beg, iterator end, value);
Calculate the cumulative sum of container elements
beg: start iterator
End: end iterator
Value: starting value (starting cumulative value, adding all subsequent values here)


Case: test the function of accumulate

#include <numeric>
#include <vector>
#include <iostream>
using namespace std;

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v;
	for (int i = 0; i <= 100; i++) {
		v.push_back(i);
	}

	int a = accumulate(v.begin(), v.end(), 0);
	int b = accumulate(v.begin(), v.end(), 1000);

	cout << "a = " << a << ", b = " << b << endl;
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


2.2 fill

Function Description: fill the container with the specified elements
Function prototype: fill(iterator beg, iterator end, value);
Fill the container with elements
beg: start iterator
End: end iterator
Value: filled value


Case: test the function of fill

#include <numeric>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{

	vector<int> v;
	v.resize(10);
	//fill
	fill(v.begin(), v.end(), 100);

	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


3, Common set algorithm

Learning objectives: master common set algorithms
Algorithm Introduction:
set_intersection / / find the intersection of two containers
set_union / / find the union of two containers
set_difference / / find the difference between two containers


3.1 set_intersection

Function Description: find the intersection of two containers
Function prototype: set_intersection(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
Find the intersection of two sets. Note that the two sets must be ordered sequences
beg1: container 1 start iterator
end1: container 1 end iterator
beg2: container 2 start iterator
end2: container 2 end iterator
dest: target container start iterator


Case: Test Set_ Function of intersection

#include <numeric>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

void myPrint(int val)
{
	cout << val << " ";
}

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
		v2.push_back(i+5);
	}
	for_each(v1.begin(), v1.end(), myPrint);
	cout << endl;
	for_each(v2.begin(), v2.end(), myPrint);
	cout << endl;

	vector<int> v3;
	//The container size is the smallest of the two containers
	v3.resize(min(v1.size(), v2.size()));
	vector<int>::iterator End = set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
	for_each(v3.begin(), End, myPrint);
	cout << endl;
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


3.2 set_intersection

Function Description: find the union of two sets
Function prototype: set_union(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
Find the union of two sets. Note: the two sets must be an ordered sequence.
beg1: container 1 start iterator
end1: container 1 end iterator
beg2: container 2 start iterator
end2: container 2 end iterator
dest: target container start iterator


Case: Test Set_ Functions of union.

#include <numeric>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

void myPrint(int val)
{
	cout << val << " ";
}

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
		v2.push_back(i+5);
	}
	for_each(v1.begin(), v1.end(), myPrint);
	cout << endl;
	for_each(v2.begin(), v2.end(), myPrint);
	cout << endl;

	vector<int> v3;
	//The new container size is the sum of the previous two container sizes
	v3.resize(v1.size() + v2.size());
	vector<int>::iterator End = set_union(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
	for_each(v3.begin(), End, myPrint);
	cout << endl;
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.


3.3 set_difference

Function Description: find the difference set of two sets
Function prototype: set_difference(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
Find the difference set of two sets. Note: the two sets must be an ordered sequence.
beg1: container 1 start iterator
end1: container 1 end iterator
beg2: container 2 start iterator
end2: container 2 end iterator
dest: target container start iterator

The definition of difference set is as follows:


Case: Test Set_ Function of difference

#include <numeric>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

void myPrint(int val)
{
	cout << val << " ";
}

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
		v2.push_back(i+5);
	}
	for_each(v1.begin(), v1.end(), myPrint);
	cout << endl;
	for_each(v2.begin(), v2.end(), myPrint);
	cout << endl;

	vector<int> v3;
	v3.resize(max(v1.size(),v2.size()));
	//Difference set of v1 and v2
	vector<int>::iterator End = set_difference(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
	for_each(v3.begin(), End, myPrint);
	cout << endl;
	//Difference set of v2 and v1
	End = set_difference(v2.begin(), v2.end(), v1.begin(), v1.end(), v3.begin());
	for_each(v3.begin(), End, myPrint);
	cout << endl;
}

int main() {
	test01();
	system("pause");

	return 0;
}

Run, the effect is as follows.

Tags: C++ data structure Algorithm Interview C

Posted by mbarmawi on Mon, 08 Aug 2022 02:51:25 +0930