Not quite equal, but emplace_back() can be better in certain situations. Let me explain the differences:

Key Differences

push_back(): Takes an object and copies/moves it into the vector

vector<pair<int,int>> v;
v.push_back(make_pair(1, 2));  // Creates pair, then moves it
v.push_back({1, 2});           // Creates pair, then moves it

emplace_back(): Constructs the object directly in the vector using the arguments you provide

vector<pair<int,int>> v;
v.emplace_back(1, 2);  // Constructs pair directly in vector

Performance Comparison

For simple types (int, long long, etc.): No difference

vector<int> v;
v.push_back(5);     // Same performance
v.emplace_back(5);  // Same performance

For complex types with expensive constructors: emplace_back() is potentially faster

vector<string> v;
v.push_back(string(1000, 'a'));  // Creates temp string, then moves
v.emplace_back(1000, 'a');       // Constructs directly, no temp

For pairs/tuples: emplace_back() is cleaner

vector<pair<int,int>> v;
v.push_back({1, 2});    // OK but creates temporary
v.emplace_back(1, 2);   // Better, direct construction

When to Use What?

• Competitive programming: Use emplace_back() for pairs/tuples (cleaner syntax), either for simple types
• Already have an object: Use push_back(obj)
• Want to construct in-place: Use emplace_back(args...)

In practice for CP, the performance difference is negligible for most cases, but emplace_back() gives cleaner code when working with pairs and complex structures!