A compact list of essential STL (Standard Template Library) headers and functions for quick revision and practice.
⚙️ <algorithm>
Commonly used functions for array and vector manipulation:
sort(first, last); // Sort elements in ascending order
reverse(first, last); // Reverse the order of elements
find(first, last, val); // Find the first occurrence of val
copy(first, last, dest); // Copy elements to another container
count(first, last, val); // Count occurrences of val
unique(first, last); // Remove consecutive duplicates
max_element(first, last); // Find the maximum element
min_element(first, last); // Find the minimum element
🧩 <vector>
🏗 Initialization
vector<int> v; // Empty vector
vector<int> v(5); // Size 5, all elements 0
vector<int> v(5, 10); // Size 5, all elements 10
vector<int> v2 = {1, 2, 3}; // Using initializer list
vector<int> v3(v2); // Copy constructor
📏 Capacity
v.size(); // Number of elements
v.capacity(); // Allocated memory size
v.empty(); // Check if vector is empty
v.resize(n); // Resize vector to n elements
v.reserve(n); // Allocate memory for n elements
v.shrink_to_fit(); // Reduce capacity to size
🔍 Element Access
v[i]; // Access element by index
v.at(i); // Safe access with bounds checking
v.front(); // First element
v.back(); // Last element
v.data(); // Pointer to internal array
✏️ Modifiers
v.push_back(x); // Add element at end
v.pop_back(); // Remove last element
v.insert(pos, val); // Insert at specific position
v.erase(pos); // Erase element at position
v.clear(); // Remove all elements
v.assign(n, val); // Replace content with n copies of val
v.swap(v2); // Swap with another vector
v.emplace(pos, val); // Construct element in place
v.emplace_back(val); // Construct element at end
🧭 Iterators
v.begin(); // Iterator to first element
v.end(); // Iterator to past-the-end
v.rbegin(); // Reverse iterator to last element
v.rend(); // Reverse iterator to before-first
v.cbegin(); // Constant iterator to first
v.cend(); // Constant iterator to past-the-end
v.crbegin(); // Constant reverse iterator to last
v.crend(); // Constant reverse iterator to before-first
🧠 Other Important STL Headers
📚 <string>
string s = "Hello";
s.length(); // Get size
s.append("!"); // Add text
s.substr(pos, len); // Get substring
s.find("l"); // Find position
s.erase(pos); // Remove characters
s.insert(pos, str); // Insert string
📋 <map> / <unordered_map>
map<int, string> m;
m[key] = value; // Insert or update
m.insert({key, value}); // Insert pair
m.erase(key); // Remove by key
m.find(key); // Find iterator to key
m.size(); // Get size
m.clear(); // Remove all
🧮 <set> / <unordered_set>
set<int> s;
s.insert(x); // Add element
s.erase(x); // Remove element
s.count(x); // Check existence
s.find(x); // Find element
s.size(); // Get number of elements
s.clear(); // Clear all
🪣 <queue> / <stack> / <priority_queue>
queue<int> q;
q.push(x); q.pop(); q.front();
stack<int> st;
st.push(x); st.pop(); st.top();
priority_queue<int> pq; // Max-heap
priority_queue<int, vector<int>, greater<int>> pq_min; // Min-heap
pq.push(x); pq.pop(); pq.top();
⚡ <pair> and <tuple>
pair<int, string> p = {1, "Ayush"};
p.first; p.second;
tuple<int, string, float> t = {1, "A", 2.5};
get<0>(t); get<1>(t); get<2>(t);