Below is a short snippet of code giving examples of basic usage of the C++ STL for handling vectors (arrays), sorting, and graphs (adjacency matrix, adjacency list).

# include<iostream># include<vector># include<algorithm># include<utility>using namespace std;int NMAX = 5000; // constraints on Nint MMAX = 100000; // constraints on Mvector <int> vv; // vectorvv.resize(n); // resizing since you get to know n during run-timefor (i = 0; i < n; i++) {cin >> vv[i];}sort(vv.begin(), vv.end()); // sort vv from begin to endvector < pair <int, int> > pairs(n); // vector of pairsint a, b;for (i = 0; i < n; i++) {cin >> pairs[i].first >> pairs[i].second;}sort(pairs.begin(), pairs.end()); // sort still worksvector <int> nodes(NMAX); // vector with NMAX elementsvector <int> nodes(NMAX, 0); // vector with NMAX elements initialized to 0int adjacency_matrix[NMAX][NMAX]; // 2D matrix NMAX x NMAXfor (int i = 0; i < m; i++) {cin >> a >> b;adjacency_matrix[a][b] = 1;adjacency_matrix[b][a] = 1; // only if graph is undirected}// neighbors of node using adjacency matrix// ( good if dense graph, for sparse graph use adjacency list )for (int i = 0; i < n; i++) {if (adjacency_matrix[node][i] == 1) {// do stuff}}// is x neighbor of y ? ( good )if ( adjacency_matrix[x][y] == 1 ) {// do stuff}vector <int> adjacency_list [NMAX]; // NMAX vectorsfor (int i = 0; i < m; m++) {cin >> a >> b;adjacency_list[a].push_back(b);adjacency_list[b].push_back(a); // only if graph is undirected}// is x neighbor of y ? ( bad, adjacency matrix is faster )for (int i = 0; i < adjacency_list[node].size() ; i++) {if (adjacency_list[x][i] == j) {// do stuff}}// neighbors of node using adjacency list ( good )for (int i = 0; i < adjacency_list[node].size() ; i++) {int neighbor = adjacency_list[node][i];// do stuff}// adjacency matrix using vectors.// overkill. not recommended. use 2D arraysvector< vector<int> > adjacency_matrix (N, vector<int>(N, 0)) ;

An in-depth STL tutorial can be found on TopCoder (it is pretty advanced though): STL part 1, STL part 2. Also, here are a couple of popular websites if you want to check what operations each thing in C++ STL supports: Learn C++, The C++ Resources Network.

Feel free to ask questions, and post additional STL usage you have found useful while solving problems. And obviously, do let me know if you notice any errors above.