C++ STL Map Container – std::map

In this instructional exercise you will find out about STL Map holder in C++ i.e., std:: map and all capacities material on it. The guide is an acquainted holder. Guide fulfils "acquainted". That implies each an incentive in the map is related to a key. All keys are novel. No two mapped qualities can have the same key. The sort of key and put away qualities may contrast. All components pursue a severe request. At the point when we embed component naturally put away in its right position. C++ STL Map Iterators that can be pertinent on map: start(): returns iterator to the start. end(): returns iterator as far as possible of the guide. rbegin(): returns turn around iterator to invert starting. rip(): returns switch iterator to turn around end. cbegin(): Returns consistent iterator to the start. cend(): Returns steady iterator as far as possible. These iterators we can use in our projects. The first thing we have to incorporate the map header record. Which is #include Let see a few capacities related to the map: Embeddings component into the map: At whatever point a component embedded into the map, size of the guide increments. Since the map contains special keys when we attempt to embed a component into the map, it generally checks whether any component previously embedded or not with this equivalent key worth. There are various ways we can embed components into the map. Strategy 1: Insert legitimately bypassing component and its comparing key. map name.insert (pair ( key, esteem )); Strategy 2: Using iterator. This profits iterator in the embedded position. map name.insert (iterator, pair (key worth, information esteem)); A model program for embeddings into the map: #include #include #include using namespace std; int main(){ map mp1; // declaring map map :: iterator it; // Inserting method 1: for (int i=0; i (i, i*10)); } // Caution: If you give any constant in place of first argument in insert. Only the first value will be inserted. Remaining will be pushed out as duplicates. // inserting method 2: it= mp1.begin(); mp1.insert(it, pair (99, 99)); // Even this was inserted at starting position, due to porperty of ordering of associative containers it sorted according to its key value and inserted at last position. it= mp1.end(); mp1.insert(it, pair (10, 10)); // printing for ( it= mp1.begin(); it!=mp1.end(); it++) { cout first; cout second; cout << endl; } return 0; } Output 0 0 1 10 2 20 3 30 4 40 10 10 99 99 Other adjustment works on map: eradicate(): We can evacuate a single component or scope of components. The impact on the map is at whatever point a worth erased from the map, its size gets diminished. swap(): swaps components of map1 to map2 and map2 to map1. Here both map1 and map2 are needed not to be of the same size. clear(): evacuates all components in the guide. It results in a guide of size 0. Model program to appear above work: #include #include #include using namespace std; int main(){ map mp1; map mp2; map :: iterator it; for (int i=0; i (i,i+10)); } // deleting element pointed by iterator it = mp1.begin(); mp1.erase(it); // key 0 deleted cout first; cout second; cout (i,i+10)); } for (int i=0; i (i,i*10)); } cout first; cout second; cout first; cout second; cout first; cout second; cout first; cout second; cout << endl; } cout << "applying clear operation" << endl; mp1.clear(); mp2.clear(); chk= mp1.empty(); if (chk == 1) cout << "map is empty by clear operation" << endl; else cout << "map is not empty"; return 0; } Output printing remaining elements after one erase operation 1 11 2 12 3 13 4 14 checking map empty or not map is empty map1 elements before swap 0 10 1 11 2 12 3 13 4 14 map2 elements before swap 0 0 1 10 2 20 3 30 4 40 map1 elements after swap 0 0 1 10 2 20 3 30 4 40 map2 elements after swap 0 10 1 11 2 12 3 13 4 14 applying clear operation map is empty by clear operation Capacities identified with limit: void(): restores a Boolean worth whether the guide is vacant or not. size(): restores the size of the guide. max_size(): restores the most extreme size a guide can have. Model program to appear above capacities: #include #include #include using namespace std; int main(){ map mp1; map :: iterator it; for(int i=0; i (i, i*10 )); } int chk = mp1.empty(); if (chk == 1) cout << " map is empty" << endl; else cout << "map contains some elements" << endl; cout << "size of the map is " ; cout << mp1.size() << endl; cout << "maximum size of the map is " ; cout << mp1.max_size() << endl; return 0; } Output map contains some elements size of the map is 5 maximum size of the map is 461168601842738790 Remark beneath on the off chance that you have questions or discovered any data erroneous in above instructional exercise for C++ STL Map holder, for example, std:: map.