// A C++ program to find a peak element
// using divide and conquer
#include <bits/stdc++.h>
using namespace std;

// A binary search based function
// that returns index of a peak element
int findPeakUtil(int arr[], int low,
				int high, int n)
{
	// Find index of middle element
	// (low + high)/2
	int mid = low + (high - low) / 2;

	// Compare middle element with its
	// neighbours (if neighbours exist)
	if ((mid == 0 || arr[mid - 1] <= arr[mid]) &&
		(mid == n - 1 || arr[mid + 1] <= arr[mid]))
		return arr[mid];

	// If middle element is not peak and its
	// left neighbour is greater than it,
	// then left half must have a peak element
	else if (mid > 0 && arr[mid - 1] > arr[mid])
		return findPeakUtil(arr, low, (mid - 1), n);

	// If middle element is not peak and its
	// right neighbour is greater than it,
	// then right half must have a peak element
	else
		return findPeakUtil(
			arr, (mid + 1), high, n);
}

// A wrapper over recursive function findPeakUtil()
int findPeak(int arr[], int n)
{
	return findPeakUtil(arr, 0, n - 1, n);
}

// Driver Code
int main()
{
	int arr[] = { 1, 3, 1,2,8,90,1, 0 };
	int n = sizeof(arr) / sizeof(arr[0]);
	cout << "First Peak point is "
		<< findPeak(arr, n);
	return 0;
}

// This code is contributed by rathbhupendra
by

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About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}