adding the emplace_back and push_back example programs

lectures/optimization/emplace_back/emplace_back_slower.cpp

@@ -0,0 +1,47 @@
+#include <iostream>
+#include <vector>
+#include <chrono>
+#include <cstring>
+
+class LargeObject {
+public:
+    // constructor allocating a large amount of memory
+    LargeObject(int size) {
+	size_ = size;
+	data_ = new char[size_];
+        // initialize data with some values
+        std::memset(data_, 'A', size_);
+    }
+
+    // copy constructor
+    LargeObject(const LargeObject& other) {
+	size_ = other.size_;
+	data_ = new char[size_];
+        std::memcpy(data_, other.data_, size_);
+    }
+
+    // destructor
+    ~LargeObject() {
+        delete[] data_;
+    }
+
+private:
+    size_t size_;
+    char* data_;
+};
+
+int main() {
+    int numElements = 1000000; // number of elements
+    int dataSize = 1024;       // size of each LargeObject's data
+
+    std::vector<LargeObject> vec;
+
+    for (size_t i = 0; i < numElements; ++i) {
+        vec.emplace_back(dataSize);	// copy constructor would get called here
+					// when a std::vector exceeds its current capacity, 
+					// it allocates a larger block of memory and copies existing elements to the new storage location. 
+					// this reallocation process involves calling the copy constructor for each existing element.
+    }
+
+    return 0;
+}