# C++ Programming Code Examples

## C++ > Sorting Searching Code Examples

### Generate All Possible Combinations of a Given List of Numbers

/* Generate All Possible Combinations of a Given List of Numbers - This algorithm print all the possible combination of each length from the given array. - The time complexity of this algorithm is O(n*(2^n)). - This algorithm takes the input of 'n' data element and prints all possible combination. - For that, it maintains a boolean array of length 'n'. - If the corresponding boolean value is true, then it prints that element. - Exit. */ #include<iostream> using namespace std; // A function to print all combination of a given length from the given array. void Combination(int a[], int reqLen, int start, int currLen, bool check[], int len) { // Return if the currLen is more than the required length. if(currLen > reqLen) return; // If currLen is equal to required length then print the sequence. else if (currLen == reqLen) { cout<<"\t"; for (int i = 0; i < len; i++) { if (check[i] == true) { cout<<a[i]<<" "; } } cout<<"\n"; return; } // If start equals to len then return since no further element left. if (start == len) { return; } // For every index we have two options. // First is, we select it, means put true in check[] and increment currLen and start. check[start] = true; Combination(a, reqLen, start + 1, currLen + 1, check, len); // Second is, we don't select it, means put false in check[] and only start incremented. check[start] = false; Combination(a, reqLen, start + 1, currLen, check, len); } int main() { int i, n; bool check[n]; cout<<"Enter the number of element array have: "; cin>>n; int arr[n]; cout<<"\n"; // Take the input of the array. for(i = 0; i < n; i++) { cout<<"Enter "<<i+1<<" element: "; cin>>arr[i]; check[i] = false; } // For each length of sub-array, call the Combination(). for(i = 1; i <= n; i++) { cout<<"\nThe combination of length "<<i<<" for the given array set:\n"; Combination(arr, i, 0, 0, check, n); } return 0; }

#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 relational operator is used to check the relationship between two operands. C++ Relational Operators are used to relate or compare given operands. Relational operations are like checking if two operands are equal or not equal, greater or lesser, etc. Relational Operators are also called Comparison Operators.

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.

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.

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 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.

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.

An array is defined as the collection of similar type of data items stored at contiguous memory locations. Arrays are the derived data type in C++ programming language which can store the primitive type of data such as int, char, double, float, etc. It also has the capability to store the collection of derived data types, such as pointers, structure, etc. The array is the simplest data structure where each data element can be randomly accessed by using its index number. C++ array is beneficial if you have to store similar elements. For example, if we want to store the marks of a student in 6 subjects, then we don't need to define different variables for the marks in the different subject. Instead of that, we can define an array which can store the marks in each subject at the contiguous memory locations.

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.

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.

Implement Gift Wrapping algorithm to find convex hull in "Two Dimensional Space". In computational geometry, the gift wrapping algorithm is an algorithm for computing the

It initializes the value current level, permutes the remaining values to the 'higher levels'. As the Assigning Action of the values reaches to the "Highest Level", it prints the permutation