C++ Programming Code Examples

/* Program to Find Closest Pair of Points in an Array */ #include <iostream> #include <cfloat> #include <cstdlib> #include <cmath> using namespace std; /* Point Declaration */ struct Point { int x, y; }; /* sort array of points according to X coordinate */ int compareX(const void* a, const void* b) { Point *p1 = (Point *)a, *p2 = (Point *)b; return (p1->x - p2->x); } /* sort array of points according to Y coordinate */ int compareY(const void* a, const void* b) { Point *p1 = (Point *)a, *p2 = (Point *)b; return (p1->y - p2->y); } /* find the distance between two points */ float dist(Point p1, Point p2) { return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y)); } /* return the smallest distance between two points */ float small_dist(Point P[], int n) { float min = FLT_MAX; for (int i = 0; i < n; ++i) { for (int j = i + 1; j < n; ++j) { if (dist(P[i], P[j]) < min) min = dist(P[i], P[j]); } } return min; } /* find the distance beween the closest points of strip of given size */ float stripClosest(Point strip[], int size, float d) { float min = d; for (int i = 0; i < size; ++i) { for (int j = i + 1; j < size && (strip[j].y - strip[i].y) < min; ++j) { if (dist(strip[i],strip[j]) < min) min = dist(strip[i], strip[j]); } } return min; } /* find the smallest distance. */ float closestUtil(Point Px[], Point Py[], int n) { if (n <= 3) return small_dist(Px, n); int mid = n / 2; Point midPoint = Px[mid]; Point Pyl[mid + 1]; Point Pyr[n - mid - 1]; int li = 0, ri = 0; for (int i = 0; i < n; i++) { if (Py[i].x <= midPoint.x) Pyl[li++] = Py[i]; else Pyr[ri++] = Py[i]; } float dl = closestUtil(Px, Pyl, mid); float dr = closestUtil(Px + mid, Pyr, n-mid); float d = min(dl, dr); Point strip[n]; int j = 0; for (int i = 0; i < n; i++) { if (abs(Py[i].x - midPoint.x) < d) strip[j] = Py[i], j++; } return min(d, stripClosest(strip, j, d)); } /* finds the smallest distance */ float closest(Point P[], int n) { Point Px[n]; Point Py[n]; for (int i = 0; i < n; i++) { Px[i] = P[i]; Py[i] = P[i]; } qsort(Px, n, sizeof(Point), compareX); qsort(Py, n, sizeof(Point), compareY); return closestUtil(Px, Py, n); } /* Main */ int main() { Point P[] = {{4, 8}, {13, 38}, {44, 50}, {8, 3}, {14, 9}, {5, 8}}; int n = sizeof(P) / sizeof(P[0]); cout << "The smallest distance is " << closest(P, n); return 0; }

/* The sizeof() is an operator in C and C++. It is an unary operator which assists a programmer in finding the size of the operand which is being used. */ #include <iostream> using namespace std; int main() { int arr[]={10,20,30,40,50}; std::cout << "Size of the array 'arr' is : "<<sizeof(arr) << std::endl; cout << "Size of char : " << sizeof(char) << endl; cout << "Size of int : " << sizeof(int) << endl; cout << "Size of short int : " << sizeof(short int) << endl; cout << "Size of long int : " << sizeof(long int) << endl; cout << "Size of float : " << sizeof(float) << endl; cout << "Size of double : " << sizeof(double) << endl; cout << "Size of wchar_t : " << sizeof(wchar_t) << endl; return 0; }

/* namespaces in C++ language */ // A C++ code to demonstrate that we can define // methods outside namespace. #include <iostream> using namespace std; // Creating a namespace namespace ns { void display(); class happy { public: void display(); }; } // Defining methods of namespace void ns::happy::display() { cout << "ns::happy::display()\n"; } void ns::display() { cout << "ns::display()\n"; } // Driver code int main() { ns::happy obj; ns::display(); obj.display(); return 0; }

/* std::min is defined in the header file <algorithm> and is used to find out the smallest of the number passed to it. It returns the first of them, if there are more than one. */ /* accept two values and return the smaller one by min() function code example. */ #include <iostream> #include <algorithm> using namespace std; // Defining the binary function bool comp(int a, int b) { return (a < b); } int main() { int a = 5; int b = 7; cout << std::min(a, b, comp) << "\n"; // Returns the first one if both the numbers // are same cout << std::min(7, 7, comp); return 0; }

/* using #include directive in C language */ #include <stdio.h> int main() { /* * C standard library printf function * defined in the stdio.h header file */ printf("I love you Clementine"); printf("I love you so much"); printf("HappyCodings"); return 0; }

/* nested loop statement in C++ language */ // C++ program that uses nested for loop to print a 2D matrix #include <bits/stdc++.h> using namespace std; #define ROW 3 #define COL 3 // Driver program int main() { int i, j; // Declare the matrix int matrix[ROW][COL] = { { 4, 8, 12 }, { 16, 20, 24 }, { 28, 32, 36 } }; cout << "Given matrix is \n"; // Print the matrix using nested loops for (i = 0; i < ROW; i++) { for (j = 0; j < COL; j++) cout << matrix[i][j]; cout << "\n"; } return 0; }

/* For Loop Statement in C++ Language */ // C++ program to find the sum of first n natural numbers // positive integers such as 1,2,3,...n are known as natural numbers #include <iostream> using namespace std; int main() { int num, sum; sum = 0; cout << "Enter a positive integer: "; cin >> num; for (int i = 1; i <= num; ++i) { sum += i; } cout << "Sum = " << sum << endl; return 0; }

/* return the absolute value of parameter by abs() function code example */ // C++ code to demonstrate the example of abs() function #include <iostream> #include <cmath> using namespace std; // main() section int main() { float x; float result; x = -10; cout<<"abs("<<x<<"): "<<abs(x)<<endl; x = -1012.232; cout<<"abs("<<x<<"): "<<abs(x)<<endl; x = 1012.232; cout<<"abs("<<x<<"): "<<abs(x)<<endl; x = -.908; cout<<"abs("<<x<<"): "<<abs(x)<<endl; return 0; }

/* If Else Statement in C++ Language */ #include <iostream> using namespace std; int main () { // local variable declaration: int a = 100; // check the boolean condition if( a < 20 ) { // if condition is true then print the following cout << "a is less than 20;" << endl; } else { // if condition is false then print the following cout << "a is not less than 20;" << endl; } cout << "value of a is : " << a << endl; return 0; }

/* Structure is a collection of variables of different data types under a single name. It is similar to a class in that, both holds a collecion of data of different data types. */ #include <iostream> using namespace std; struct Person { char name[50]; int age; float salary; }; int main() { Person p1; cout << "Enter Full name: "; cin.get(p1.name, 50); cout << "Enter age: "; cin >> p1.age; cout << "Enter salary: "; cin >> p1.salary; cout << "\nDisplaying Information." << endl; cout << "Name: " << p1.name << endl; cout <<"Age: " << p1.age << endl; cout << "Salary: " << p1.salary; return 0; }

/* compute square root by sqrt() math function code example */ // C++ code to demonstrate the example of sqrt() function #include <iostream> #include <cmath> using namespace std; // main code section int main() { float x; //input the value cout<<"Enter a number: "; cin>>x; // calculate the square root float result = sqrt(x); cout<<"square root of "<<x<<" is = "<<result; cout<<endl; return 0; }

/* The eof() method of ios class in C++ is used to check if the stream is has raised any EOF (End Of File) error. It means that this function will check if this stream has its eofbit set. */ // C++ code example to demonstrate the working of eof() function #include <iostream> #include <fstream> int main () { std::ifstream is("example.txt"); char c; while (is.get(c)) std::cout << c; if (is.eof()) std::cout << "[EoF reached]\n"; else std::cout << "[error reading]\n"; is.close(); return 0; }

/* Perhaps you have warm memories of doing arithmetic drills in grade school. You can give that same pleasure to your computer. C++ uses operators to do arithmetic. It provides operators for five basic arithmetic calculations: addition, subtraction, multiplication, division, and taking the modulus. Each of these operators uses two values (called operands) to calculate a final answer. Together, the operator and its operands constitute an expression. */ #include <iostream> using namespace std; int main() { int a, b; a = 7; b = 2; // printing the sum of a and b cout << "a + b = " << (a + b) << endl; // printing the difference of a and b cout << "a - b = " << (a - b) << endl; // printing the product of a and b cout << "a * b = " << (a * b) << endl; // printing the division of a by b cout << "a / b = " << (a / b) << endl; // printing the modulo of a by b cout << "a % b = " << (a % b) << endl; return 0; }

/* arrays in C++ Language */ #include <iostream> using namespace std; int main() { // initialize an array without specifying size double numbers[] = {7, 5, 6, 12, 35, 27}; double sum = 0; double count = 0; double average; cout << "The numbers are: "; // print array elements // use of range-based for loop for (const double &n : numbers) { cout << n << " "; // calculate the sum sum += n; // count the no. of array elements ++count; } // print the sum cout << "\nTheir Sum = " << sum << endl; // find the average average = sum / count; cout << "Their Average = " << average << endl; return 0; }

/* The operator ! is the C++ operator for the Boolean operation NOT. It has only one operand, to its right, and inverts it, producing false if its operand is true, and true if its operand is false. Basically, it returns the opposite Boolean value of evaluating its operand. The logical operators && and || are used when evaluating two expressions to obtain a single relational result. The operator && corresponds to the Boolean logical operation AND, which yields true if both its operands are true, and false otherwise. */ #include <iostream> using namespace std; main() { int a = 5; int b = 20; int c ; if(a && b) { cout << "Line 1 - Condition is true"<< endl ; } if(a || b) { cout << "Line 2 - Condition is true"<< endl ; } /* Let's change the values of a and b */ a = 0; b = 10; if(a && b) { cout << "Line 3 - Condition is true"<< endl ; } else { cout << "Line 4 - Condition is not true"<< endl ; } if(!(a && b)) { cout << "Line 5 - Condition is true"<< endl ; } return 0; }

/* The qsort() function sorts the given array pointed at by the base pointer. */ /* sort a given array in ascending order using Quicksort algorithm by qsort() function code example. */ #include <iostream> #include <cstdlib> using namespace std; int compare(const void* a, const void* b) { const int* x = (int*) a; const int* y = (int*) b; if (*x > *y) return 1; else if (*x < *y) return -1; return 0; } int main() { const int num = 10; int arr[num] = {9,4,19,2,7,9,5,15,23,3}; cout << "Before sorting" << endl; for (int i=0; i<num; i++) cout << arr[i] << " "; qsort(arr,num,sizeof(int),compare); cout << endl << endl; cout << "After sorting" << endl; for (int i=0; i<num; i++) cout << arr[i] << " "; return 0; }

/* simple code example by main() function in C++ */ #include <iostream> using namespace std; int main() { int day = 4; switch (day) { case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; break; case 3: cout << "Wednesday"; break; case 4: cout << "Thursday"; break; case 5: cout << "Friday"; break; case 6: cout << "Saturday"; break; case 7: cout << "Sunday"; break; } return 0; }