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;
}
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