C++ Programming Code Examples
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C++ Program to Represent Graph Using 2D Arrays
/* C++ Program to Represent Graph Using 2D Arrays
- This algorithm represents a graph using 2D arrays.
- This method of representing graphs is not efficient.
- The time complexity of this algorithm is O(v*v).
- This algorithm takes the input of the number of vertex and edges.
- Take the input of connected vertex pairs.
- Print the graph using 2D arrays.
- Exit. */
#include<iostream>
#include<iomanip>
using namespace std;
// A function to print the matrix.
void PrintMat(int **mat, int n)
{
int i, j;
cout<<"\n\n"<<setw(4)<<"";
for(i = 0; i < n; i++)
cout<<setw(3)<<"("<<i+1<<")";
cout<<"\n\n";
// Print 1 if the corresponding vertexes are connected otherwise 0.
for(i = 0; i < n; i++)
{
cout<<setw(3)<<"("<<i+1<<")";
for(j = 0; j < n; j++)
{
cout<<setw(4)<<mat[i][j];
}
cout<<"\n\n";
}
}
int main()
{
int i, v, e, j, v1, v2;
// take the input of the number of edges.
cout<<"Enter the number of vertexes of the graph: ";
cin>>v;
// Dynamically declare graph.
int **graph;
graph = new int*[v];
for(i = 0; i < v; i++)
{
graph[i] = new int[v];
for(j = 0; j < v; j++)graph[i][j] = 0;
}
cout<<"\nEnter the number of edges of the graph: ";
cin>>e;
// Take the input of the adjacent vertex pairs of the given graph.
for(i = 0; i < e; i++)
{
cout<<"\nEnter the vertex pair for edge "<<i+1;
cout<<"\nV(1): ";
cin>>v1;
cout<<"V(2): ";
cin>>v2;
graph[v1-1][v2-1] = 1;
graph[v2-1][v1-1] = 1;
}
// Print the 2D array representation of the graph.
PrintMat(graph, v);
}
Allocate storage space. Default allocation functions (single-object form). A new operator is used to create the object while a delete operator is used to delete the object. When the object is created by using the new operator, then the object will exist until we explicitly use the delete operator to delete the object. Therefore, we can say that the lifetime of the object is not related to the block structure of the program.
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A program shall contain a global function named main, which is the designated start of the program in hosted environment. main() function is the entry point of any C++ program. It is the point at which execution of program is started. When a C++ program is executed, the execution control goes directly to the main() function. Every C++ program have a main() function.
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An array is a collection of data items, all of the same type, accessed using a common name. A one-dimensional array is like a list; A two dimensional array is like a table; The C++ language places no limits on the number of dimensions in an array, though specific implementations may. Some texts refer to one-dimensional arrays as vectors, two-dimensional arrays as matrices, and use the general term arrays when the number of dimensions is unspecified or unimportant. (2D) array in C++ programming is also known as matrix. A matrix can be represented as a table of rows and columns. In C/C++, we can define multi dimensional arrays in simple words as array of arrays. Data in multi dimensional arrays are stored in tabular form (in row major order).
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Set field width. Sets the field width to be used on output operations. The C++ function std::setw behaves as if member width were called with n as argument on the stream on which it is inserted/extracted as a manipulator (it can be inserted/extracted on input streams or output streams). It is used to sets the field width to be used on output operations. This manipulator is declared in header <iomanip>. This method accepts n as a parameter which is the integer argument corresponding to which the field width is to be set. This function returns an object of unspecified type. The setw function should only be used as a stream manipulator.
Problem takes E edges as input and outputs vertex cover of the graph, implementing the following heuristic. There is no "Polynomial" time algorithm "invented up to date" to find
