C++ Programming

string

• .length() size() - return the length
• [] - get/set value of string
• .reserve(size) - reserve size for the string
• += - append
• append(string) - append another string
• insert(index, string) - insert string at index
• substr(start, size) - get a substring of size from start index
• std::to_string(int) - integer to string
• stoi(string) - string to integer
• stof(string) - string to float

arrays, raw arrays

• [] - get/set value at a index
• sizeof(arr)/sizeof(arr[0]) - get size of arr
• can be of only fixed size, int arr[SIZE]
• for variable size use pointers, int *arr = new int[n]; delete[] arr;
• fill array with a particular value, memset(arr, 0, sizeof(arr));

vector

• push_back(value) - add value to end of vector
• [index] - get/set value at index
• size() - return the size of vector

unordered_map and map

• [index] - get/set value for a key
• find(key) - find if key is present in map, return map.end() iterator if not present
• erase(key) - remove element from the map
• clear() - remove all elements
• size() - return total elements in the map

unordered_set and set

• insert(value) - insert value in set
• erase(value) - erase value from set
• find(value) - find value in set, if not present return set.end()
• contains(value) - return true if value exists
• size() - return total elements in the set

stack

• push(value) - push values in the stack
• pop() - remove top element from the stack
• top() - return top element form the stack
• empty() - return true if stack is empty
• size() - return number of total elements in the stack

queue

• push(value) - push value at back of queue
• pop() - remove value from front of queue
• front() - return the element at front of queue
• back() - return the element at end of queue
• empty() - return if queue is empty
• size() - return the size of the queue

priority_queue

• how to create for pq for particular type
  • priority_queue<type, vector<type>, TypeComparator>
  • struct TypeComparator {bool operator()(type a, type b) {return a > b; // custom logic }};
• by default max heap is there
  • for min heap priority_queue<int, vector<int>, greater<int>> min_heap;
• push(value) - push value and maintain in heap
• pop() - remove the largest value(depending upon how you created) form the heap
• top() - return the top element
• empty() - check if heap is empty
• size() - return the number of elements

deque - double ended queue

• push_front(value) - insert value at front
• push_back(value) - insert value at back
• pop_front()
• pop_back()
• front()
• back()
• size()

bitset

• bitset<SIZE> bit(value) - create bitset of size with value
• [index] - get bit value at index
• set(index) - set bit at index, i.e. set to 1
• reset(index) - unset bit at index, i.e. set to 0
• flip(index) - flip the bit at index
• count() - return the number of bit set to 1
• any() - check if any bit is set
• none() - check if no bit is set
• test(index) - check if bit at index is set

list - double linked list

• size()

unordered_multimap multimap

• can contains same multiple items