Added solution for maximise the array

Author: sunilkumarmaurya786693

interviewbits solution/maximiseDifference.cpp

@@ -0,0 +1,132 @@
+// Maximize difference between the Sum of the two halves of the Array 
+// after removal of N elements
+
+
+// Given an integer N and array arr[] consisting of 3 * N integers, the task is to find the maximum difference between first half and second half of the array after the removal of exactly N elements from the array.
+
+// Examples:
+
+// Input: N = 2, arr[] = {3, 1, 4, 1, 5, 9}
+// Output: 1
+// Explanation:
+// Removal of arr[1] and arr[5] from the array maximizes the difference = (3 + 4) – (1 + 5) = 7 – 6 = 1.
+
+// Input: N = 1, arr[] = {1, 2, 3}
+// Output: -1
+
+
+#include <bits/stdc++.h>
+using namespace std;
+
+// Function to print the maximum difference
+// possible between the two halves of the array
+long long FindMaxDif(vector<long long> a, int m)
+{
+	int n = m / 3;
+
+	vector<long long> l(m + 5), r(m + 5);
+
+	// Stores n maximum values from the start
+	multiset<long long> s;
+
+	for (int i = 1; i <= m; i++) {
+
+		// Insert first n elements
+		if (i <= n) {
+
+			// Update sum of largest n
+			// elements from left
+			l[i] = a[i - 1] + l[i - 1];
+			s.insert(a[i - 1]);
+		}
+
+		// For the remaining elements
+		else {
+			l[i] = l[i - 1];
+
+			// Obtain minimum value
+			// in the set
+			long long d = *s.begin();
+
+			// Insert only if it is greater
+			// than minimum value
+			if (a[i - 1] > d) {
+
+				// Update sum from left
+				l[i] -= d;
+				l[i] += a[i - 1];
+
+				// Remove the minimum
+				s.erase(s.find(d));
+
+				// Insert the current element
+				s.insert(a[i - 1]);
+			}
+		}
+	}
+
+	// Clear the set
+	s.clear();
+
+	// Store n minimum elements from the end
+	for (int i = m; i >= 1; i--) {
+
+		// Insert the last n elements
+		if (i >= m - n + 1) {
+
+			// Update sum of smallest n
+			// elements from right
+			r[i] = a[i - 1] + r[i + 1];
+			s.insert(a[i - 1]);
+		}
+
+		// For the remaining elements
+		else {
+
+			r[i] = r[i + 1];
+
+			// Obtain the minimum
+			long long d = *s.rbegin();
+
+			// Insert only if it is smaller
+			// than maximum value
+			if (a[i - 1] < d) {
+
+				// Update sum from right
+				r[i] -= d;
+				r[i] += a[i - 1];
+
+				// Remove the minimum
+				s.erase(s.find(d));
+
+				// Insert the new element
+				s.insert(a[i - 1]);
+			}
+		}
+	}
+
+	long long ans = -9e18L;
+
+	for (int i = n; i <= m - n; i++) {
+
+		// Compare the difference and
+		// store the maximum
+		ans = max(ans, l[i] - r[i + 1]);
+	}
+
+	// Return the maximum
+	// possible difference
+	return ans;
+}
+
+// Driver Code
+int main()
+{
+
+	vector<long long> vtr = { 3, 1, 4, 1, 5, 9 };
+	int n = vtr.size();
+
+	cout << FindMaxDif(vtr, n);
+
+	return 0;
+}