Create implement_upper_and_lower_bound.cpp

implement_upper_and_lower_bound.cpp

@@ -0,0 +1,93 @@
+// implementation of upper_bound() and lower_bound() with help of binary search
+// Time Complexitcy will be : O(log n)
+
+#include<iostream>
+#include<vector>
+#include<algorithm>
+
+using namespace std;
+
+// function to calculate lower_bound()
+int lower_bound(vector<int> &v , int element)
+{
+	int lo = 0 , hi = v.size() - 1;
+	int mid;
+
+	while(hi - lo > 1)
+	{
+		mid = (lo+hi)/2;
+		if(v[mid] < element)
+		{
+			lo = mid+1;
+		}
+		else
+		{
+			hi = mid;
+		}
+	}
+	if(v[lo]>=element) return lo;
+	if(v[hi]>=element) return hi;
+	return -1;
+}
+
+// funciton to calculate upper_bound()
+int upper_bound(vector<int> &v , int element)
+{
+	int lo = 0 , hi = v.size()-1 ;
+	int mid;
+
+	while(hi-lo>1)
+	{
+		mid = (lo+hi)/2;
+		if(v[mid] <= element)
+		{
+			lo = mid+1;
+		}
+		else
+		{
+			hi = mid;
+		}
+	}
+	if(v[lo]>element) return lo;
+	else if(v[hi]>element) return hi;
+	return -1;
+}
+
+int main()
+{
+	int n,to_find,lower_index,upper_index;
+	cin>>n;
+
+	vector<int> arr(n);
+	//reading values of vector
+	for(int i=0 ; i<n ; ++i)
+	{
+		cin>>arr[i];
+	}
+  //you need to sort the vector/ array if you want to apply lower_bound() , upper_bound()
+  sort(arr.begin(),arr.end());
+	cout<<"Enter element to find : ";
+	cin>>to_find;
+
+	lower_index = lower_bound(arr,to_find); // function calling
+
+	if(lower_index == -1)
+	{
+		cout<<"Lower bound does not exists "<<endl;
+	}
+	else
+	{
+		cout<<"Found at : "<<lower_index << " " <<"and value at that index is : "<<arr[lower_index]<<endl;
+
+	}
+
+	upper_index = upper_bound(arr,to_find); // function calling
+
+	if(upper_index == -1)
+		cout<<"Upper bound does not exists"<<endl;
+	else
+		cout<<"Found at: "<<upper_index<<" and value at that index is : "<<arr[upper_index]<<endl;
+	return 0;
+}
+
+// we can also use inbuit function upper_bound() and lower_bound() to check our functions