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Merge pull request #3440 from gerymate/master
[C++/en] Move section about containers to its logical place
This commit is contained in:
Divay Prakash
GitHub
commit
3ba9536776
@ -809,7 +809,103 @@ void doSomethingWithAFile(const std::string& filename)
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// all automatically destroy their contents when they fall out of scope.
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// - Mutexes using lock_guard and unique_lock
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// containers with object keys of non-primitive values (custom classes) require
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/////////////////////
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// Containers
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/////////////////////
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// Containers or the Standard Template Library are some predefined templates.
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// They manage the storage space for its elements and provide
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// member functions to access and manipulate them.
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// Few containers are as follows:
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// Vector (Dynamic array)
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// Allow us to Define the Array or list of objects at run time
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#include <vector>
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string val;
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vector<string> my_vector; // initialize the vector
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cin >> val;
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my_vector.push_back(val); // will push the value of 'val' into vector ("array") my_vector
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my_vector.push_back(val); // will push the value into the vector again (now having two elements)
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// To iterate through a vector we have 2 choices:
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// Either classic looping (iterating through the vector from index 0 to its last index):
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for (int i = 0; i < my_vector.size(); i++) {
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cout << my_vector[i] << endl; // for accessing a vector's element we can use the operator []
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}
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// or using an iterator:
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vector<string>::iterator it; // initialize the iterator for vector
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for (it = my_vector.begin(); it != my_vector.end(); ++it) {
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cout << *it << endl;
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}
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// Set
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// Sets are containers that store unique elements following a specific order.
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// Set is a very useful container to store unique values in sorted order
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// without any other functions or code.
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#include<set>
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set<int> ST; // Will initialize the set of int data type
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ST.insert(30); // Will insert the value 30 in set ST
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ST.insert(10); // Will insert the value 10 in set ST
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ST.insert(20); // Will insert the value 20 in set ST
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ST.insert(30); // Will insert the value 30 in set ST
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// Now elements of sets are as follows
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// 10 20 30
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// To erase an element
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ST.erase(20); // Will erase element with value 20
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// Set ST: 10 30
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// To iterate through Set we use iterators
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set<int>::iterator it;
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for(it=ST.begin();it<ST.end();it++) {
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cout << *it << endl;
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}
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// Output:
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// 10
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// 30
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// To clear the complete container we use Container_name.clear()
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ST.clear();
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cout << ST.size(); // will print the size of set ST
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// Output: 0
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// NOTE: for duplicate elements we can use multiset
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// NOTE: For hash sets, use unordered_set. They are more efficient but
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// do not preserve order. unordered_set is available since C++11
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// Map
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// Maps store elements formed by a combination of a key value
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// and a mapped value, following a specific order.
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#include<map>
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map<char, int> mymap; // Will initialize the map with key as char and value as int
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mymap.insert(pair<char,int>('A',1));
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// Will insert value 1 for key A
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mymap.insert(pair<char,int>('Z',26));
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// Will insert value 26 for key Z
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// To iterate
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map<char,int>::iterator it;
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for (it=mymap.begin(); it!=mymap.end(); ++it)
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std::cout << it->first << "->" << it->second << '\n';
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// Output:
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// A->1
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// Z->26
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// To find the value corresponding to a key
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it = mymap.find('Z');
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cout << it->second;
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// Output: 26
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// NOTE: For hash maps, use unordered_map. They are more efficient but do
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// not preserve order. unordered_map is available since C++11.
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// Containers with object keys of non-primitive values (custom classes) require
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// compare function in the object itself or as a function pointer. Primitives
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// have default comparators, but you can override it.
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class Foo {
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@ -828,6 +924,7 @@ std::map<Foo, int, compareFunction> fooMap;
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fooMap[Foo(1)] = 1;
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fooMap.find(Foo(1)); //true
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///////////////////////////////////////
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// Lambda Expressions (C++11 and above)
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///////////////////////////////////////
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@ -994,101 +1091,6 @@ cout << get<3>(concatenated_tuple) << "\n"; // prints: 15
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cout << get<5>(concatenated_tuple) << "\n"; // prints: 'A'
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/////////////////////
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// Containers
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/////////////////////
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// Containers or the Standard Template Library are some predefined templates.
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// They manage the storage space for its elements and provide
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// member functions to access and manipulate them.
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// Few containers are as follows:
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// Vector (Dynamic array)
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// Allow us to Define the Array or list of objects at run time
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#include <vector>
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string val;
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vector<string> my_vector; // initialize the vector
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cin >> val;
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my_vector.push_back(val); // will push the value of 'val' into vector ("array") my_vector
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my_vector.push_back(val); // will push the value into the vector again (now having two elements)
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// To iterate through a vector we have 2 choices:
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// Either classic looping (iterating through the vector from index 0 to its last index):
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for (int i = 0; i < my_vector.size(); i++) {
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cout << my_vector[i] << endl; // for accessing a vector's element we can use the operator []
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}
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// or using an iterator:
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vector<string>::iterator it; // initialize the iterator for vector
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for (it = my_vector.begin(); it != my_vector.end(); ++it) {
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cout << *it << endl;
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}
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// Set
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// Sets are containers that store unique elements following a specific order.
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// Set is a very useful container to store unique values in sorted order
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// without any other functions or code.
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#include<set>
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set<int> ST; // Will initialize the set of int data type
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ST.insert(30); // Will insert the value 30 in set ST
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ST.insert(10); // Will insert the value 10 in set ST
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ST.insert(20); // Will insert the value 20 in set ST
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ST.insert(30); // Will insert the value 30 in set ST
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// Now elements of sets are as follows
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// 10 20 30
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// To erase an element
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ST.erase(20); // Will erase element with value 20
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// Set ST: 10 30
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// To iterate through Set we use iterators
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set<int>::iterator it;
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for(it=ST.begin();it<ST.end();it++) {
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cout << *it << endl;
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}
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// Output:
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// 10
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// 30
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// To clear the complete container we use Container_name.clear()
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ST.clear();
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cout << ST.size(); // will print the size of set ST
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// Output: 0
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// NOTE: for duplicate elements we can use multiset
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// NOTE: For hash sets, use unordered_set. They are more efficient but
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// do not preserve order. unordered_set is available since C++11
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// Map
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// Maps store elements formed by a combination of a key value
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// and a mapped value, following a specific order.
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#include<map>
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map<char, int> mymap; // Will initialize the map with key as char and value as int
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mymap.insert(pair<char,int>('A',1));
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// Will insert value 1 for key A
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mymap.insert(pair<char,int>('Z',26));
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// Will insert value 26 for key Z
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// To iterate
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map<char,int>::iterator it;
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for (it=mymap.begin(); it!=mymap.end(); ++it)
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std::cout << it->first << "->" << it->second << '\n';
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// Output:
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// A->1
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// Z->26
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// To find the value corresponding to a key
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it = mymap.find('Z');
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cout << it->second;
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// Output: 26
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// NOTE: For hash maps, use unordered_map. They are more efficient but do
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// not preserve order. unordered_map is available since C++11.
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///////////////////////////////////
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// Logical and Bitwise operators
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//////////////////////////////////
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