# C++ Programming Code Examples

## C++ > Sorting Searching Code Examples

### Find the peak element of an array using Binary Search approach

/* Find the peak element of an array using Binary Search approach - Using binary search approach one of the peaks in the array can be found. - It returns the first peak found as a result. - The time complexity of the algorithm is O(log(n)). - Implement the binary search to find a peak in the array. - If the middle element is more than its both neighbors, then it is the peak. - Otherwise, split the array and check the same. - Exit. */ #include<iostream> using namespace std; // A function implementing Binary search approach to find a peak. int PeakSearch(int a[], int start, int end) { int i, mid; // Assigning middle of the array. mid = (end+start+1)/2; // If mid is at boundary index of the array sub-part, and higher than its only neighbor the mid is the peak of array. if((a[mid] > a[mid+1] && mid == start)||(a[mid] > a[mid-1] && mid == end)) { return a[mid]; } // If mid is higher than its neighbors then it is the peak element. else if(a[mid] > a[mid-1] && a[mid] > a[mid+1]) { return a[mid]; } // If right neighbor is higher then right subpart must have a peak. else if(a[mid] <= a[mid+1]) { return PeakSearch(a, mid+1, end); } // If left neighbor is higher then left subpart must have a peak. else if(a[mid] <= a[mid-1]) { return PeakSearch(a, start,mid-1); } } int main() { int n, i, peak; cout<<"\nEnter the number of data element: "; cin>>n; int arr[n]; // Take data input. for(i = 0; i < n; i++) { cout<<"Enter element "<<i+1<<": "; cin>>arr[i]; } // Get the peak of the array. peak = PeakSearch(arr, 0, n-1); // Print the result. cout<<"\nThe peak element of the given array is: "<<peak; return 0; }

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.

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.

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.

Search range for subsequence. Searches the range [first1,last1) for the first occurrence of the sequence defined by [first2,last2), and returns an iterator to its first element, or last1 if no occurrences are found. The elements in both ranges are compared sequentially using operator== (or pred, in version (2)): A subsequence of [first1,last1) is considered a match only when this is true for all the elements of [first2,last2). This function returns the first of such occurrences. For an algorithm that returns the last instead, see find_end. The function shall not modify any of its arguments.

Compute natural logarithm. Returns the natural logarithm of x. The natural logarithm is the base-e logarithm: the inverse of the natural exponential function (exp). For common (base-10) logarithms, see log10. The C/C++ library function double log(double x) returns the natural logarithm (base-e logarithm) of x. Function returns natural logarithm of x. If x is negative, it causes a domain error. If x is zero, it may cause a pole error (depending on the library implementation).

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.

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:

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.

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.

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.

#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.

A "Recursive Function" to print 'DFS' starting from v. Returns reverse ('or transpose') of this graph. Add edge to connect v and w. Check if Graph is Connected and display 'The Graph is

It's used in switch case control structure after the case blocks. Generally all cases in switch case are followed by a "Break Statement" to avoid the subsequent cases (see the example

Function to insert a node in the tree. Inorder recursive & nonrecursive traversal. 'Preorder' recursive & nonrecursive traversal. 'Postrder' recursive traversal. Postorder non recursive

To check whether the input alphabet is vowel or not a vowel in C++, Enter a Character, then check the character for Vowel. The character is vowel, only if it's equal to a, A, e, E, i, I, o, O

To list and "display/print" all the files present inside the current directory in The C++, use a pointer say dir of DIR and the pointer say pdir of dirent to open and "read directory" to print