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C++ Programming Code Examples

C++ > Computer Graphics Code Examples

Perform Edge Coloring to the Line Graph of an Input Graph

/* Perform Edge Coloring to the Line Graph of an Input Graph - This algorithm performs edge coloring to the line graph of an input graph. - A line graph can be generated from the given graph by assuming edge as vertex and vertex as edges between the vertex to form line graph. - This algorithm takes the input of the number of vertexes and the number of edges in the graph. - It takes the input of vertex pairs for the given number of edges. - It generates a line graph for the given graph. - Then for the generated line graph, it assigns a color to edges without assigning the same color to two adjacent edges. - Exit. */ #include<iostream> using namespace std; // A function to generate line graph from a given graph. int GenerateLineGraph(int edge[][2], char LineEdge[][3], int e) { int i, count = 0, j, NOV; char ch; // Loop to assign a valid color to every edge 'i'. for(i = 0; i < e; i++) { for(j = i+1; j < e; j++) { // Check the colors of the edges adjacent to the edge i. if(edge[j][0] == edge[i][0] || edge[j][0] == edge[i][1] || edge[j][1] == edge[i][0] || edge[j][1] == edge[i][1]) { LineEdge[count][0] = 'a'+i; LineEdge[count][1] = 'a'+j; LineEdge[count][2] = 0; count++; } } } NOV = count; // Print the adjacency list representation of the graph. cout<<"\n\nThe adjacency list representation for the given graph: "; for(i = 0; i < e; i++) { count = 0; // For each vertex print, its adjacent vertex. ch = 'a'+i; cout<<"\n\t"<<ch<<"-> { "; for(j = 0; j < NOV; j++) { if(LineEdge[j][0] == i+'a') { cout<<LineEdge[j][1]<<" "; count++; } else if(LineEdge[j][1] == i+'a') { cout<<LineEdge[j][0]<<" "; count++; } else if(j == e-1 && count == 0) cout<<"Isolated Vertex!"; } cout<<" }"; } return NOV; } // A function to color edges of the graph. void EdgeColoring(char edge[][3], int e) { int i, col, j; // Loop to assign a valid color to every edge 'i'. for(i = 0; i < e; i++) { col = 1; flag: // Assign a color and then check its validity. edge[i][2] = col; for(j = 0; j < e; j++) { if(j == i) continue; // Check the colors of the edges adjacent to the edge i. if(edge[j][0] == edge[i][0] || edge[j][0] == edge[i][1] || edge[j][1] == edge[i][0] || edge[j][1] == edge[i][1]) { // If the color matches then goto line 11 and assign next color to the edge and check again. if(edge[j][2] == edge[i][2]) { col++; goto flag; } } } } } int main() { int i, v, e, j, max = -1; char ch = 'a'; // take the input of the number of vertex and edges. cout<<"Enter the number of vertexes of the graph: "; cin>>v; cout<<"Enter the number of edges of the graph: "; cin>>e; int edge[e][2]; char LineEdge[e*e][3]; // 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 '"<<ch++<<"'"; cout<<"\nV(1): "; cin>>edge[i][0]; cout<<"V(2): "; cin>>edge[i][1]; } // Generate line graph. e = GenerateLineGraph(edge, LineEdge, e); // Color The line graph. EdgeColoring(LineEdge , e); // Print the color of edges of line graph. for(i = 0; i < e; i++) cout<<"\nThe color of the edge between vertex V(1):"<<LineEdge[i][0]<<" and V(2):"<<LineEdge[i][1]<<" is: color"<<0+LineEdge[i][2]<<"."; }

C supports nesting of loops in C. Nesting of loops is the feature in C that allows the looping of statements inside another loop. Any number of loops can be defined inside another loop, i.e., there is no restriction for defining any number of loops. The nesting level can be defined at n times. You can define any type of loop inside another loop; for example, you can define 'while' loop inside a 'for' loop. A loop inside another loop is called a nested loop. The depth of nested loop depends on the complexity of a problem. We can have any number of nested loops as required. Consider a nested loop where the outer loop runs n times and consists of another loop inside it. The inner loop runs m times. Then, the total number of times the inner loop runs during the program execution is n*m.

Consider a situation, when we have two persons with the same name, jhon, in the same class. Whenever we need to differentiate them definitely we would have to use some additional information along with their name, like either the area, if they live in different area or their mother's or father's name, etc. Same situation can arise in your C++ applications. For example, you might be writing some code that has a function called xyz() and there is another library available which is also having same function xyz(). Now the compiler has no way of knowing which version of xyz() function you are referring to within your code.

The cout is a predefined object of ostream class. It is connected with the standard output device, which is usually a display screen. The cout is used in conjunction with stream insertion operator (<<) to display the output on a console. On most program environments, the standard output by default is the screen, and the C++ stream object defined to access it is cout. The "c" in cout refers to "character" and "out" means "output". Hence cout means "character output". The cout object is used along with the insertion operator << in order to display a stream of characters.

In computer programming, loops are used to repeat a block of code. For example, when you are displaying number from 1 to 100 you may want set the value of a variable to 1 and display it 100 times, increasing its value by 1 on each loop iteration. When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop. A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.

In computer programming, we use the if statement to run a block code only when a certain condition is met. An if statement can be followed by an optional else statement, which executes when the boolean expression is false. There are three forms of if...else statements in C++: • if statement, • if...else statement, • if...else if...else statement, The if statement evaluates the condition inside the parentheses ( ). If the condition evaluates to true, the code inside the body of if is executed. If the condition evaluates to false, the code inside the body of if is skipped.

Continue statement is used inside loops. Whenever a continue statement is encountered inside a loop, control directly jumps to the beginning of the loop for next iteration, skipping the execution of statements inside loop's body for the current iteration. The continue statement works somewhat like the break statement. Instead of forcing termination, however, continue forces the next iteration of the loop to take place, skipping any code in between. For the for loop, continue causes the conditional test and increment portions of the loop to execute. For the while and do...while loops, program control passes to the conditional tests.

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).

The if...else statement executes two different codes depending upon whether the test expression is true or false. Sometimes, a choice has to be made from more than 2 possibilities. The if...else ladder allows you to check between multiple test expressions and execute different statements. In C/C++ if-else-if ladder helps user decide from among multiple options. The C/C++ if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the C else-if ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.

Logical Operators are used to compare and connect two or more expressions or variables, such that the value of the expression is completely dependent on the original expression or value or variable. We use logical operators to check whether an expression is true or false. If the expression is true, it returns 1 whereas if the expression is false, it returns 0. Assume variable A holds 1 and variable B holds 0:

In C++, goto is a jump statement and sometimes also referred as unconditional jump statement. It can be used to jump from goto to a labeled statement within the same function. The target label must be within the same file and context. Please note that the use of goto statement is highly discouraged in any programming language because it makes difficult to trace the control flow of a program, making hard to understand and modify the program.

#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program.

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.

The cin object is used to accept input from the standard input device i.e. keyboard. It is defined in the iostream header file. C++ cin statement is the instance of the class istream and is used to read input from the standard input device which is usually a keyboard. The extraction operator(>>) is used along with the object cin for reading inputs. The extraction operator extracts the data from the object cin which is entered using the keyboard. The "c" in cin refers to "character" and "in" means "input". Hence cin means "character input". The cin object is used along with the extraction operator >> in order to receive a stream of characters.

Finding the smallest item in the tree. Return smallest item or 'INFINITY' if empty. Find the largest item in the tree. "Return the Largest" item or INFINITY if empty. Find item x in the


'Constructors with parameters' are known as "Parameterized Constructors". So these type of constructor allows us to "pass arguments" while object creation. Lets see how they look:

This algorithm takes the input of the number of 'vertex and edges'. Then it takes the input of connected vertex pairs. Print the incidence list representation of the graph. And for each


Example to print all 'prime numbers' between two numbers in C++ Language. This problem is solved using nested for loop and if...else. In this program, the while loop is iterated times.