Create MaximumSubarrayProblem.java

Algorithms/CountingInversionProblem.java

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+import java.util.Scanner;
+
+public class CountingInversionProblem {
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		System.out.println("Enter the no. of elements : ");
+		int n = sc.nextInt();
+
+		System.out.println("Enter " + n + " integers");
+		int[] numbers = new int[n];
+		for (int i = 0; i < n; i++) {
+
+			numbers[i] = sc.nextInt();
+		}
+		System.out.println("Given Array is ");
+		printArray(numbers);
+
+		int totalInversions = countingInversionUsingMergeSort(numbers, 0, n - 1);
+		System.out.println("No. Of Inversions are : " + totalInversions);
+
+	}
+
+	static void printArray(int arr[]) {
+		int n = arr.length;
+		for (int i = 0; i < n; ++i)
+			System.out.print(arr[i] + " ");
+		System.out.println();
+	}
+
+	static int countingInversionUsingMergeSort(int arr[], int l, int r) {
+		int inversionCount = 0;
+		if (l < r) {
+			int m = (l + r) / 2;
+
+			inversionCount = countingInversionUsingMergeSort(arr, l, m);
+			inversionCount = inversionCount + countingInversionUsingMergeSort(arr, m + 1, r);
+			inversionCount = inversionCount + merge(arr, l, m, r);
+
+		}
+		return inversionCount;
+	}
+
+	static int merge(int arr[], int l, int m, int r) {
+		int count = 0;
+		int n1 = m - l + 1;
+		int n2 = r - m;
+		int L[] = new int[n1];
+		int R[] = new int[n2];
+
+		for (int i = 0; i < n1; i++) {
+			L[i] = arr[l + i];
+		}
+		for (int i = 0; i < n2; i++) {
+			R[i] = arr[m + 1 + i];
+		}
+
+		int i = 0, j = 0;
+		int k = l;
+		while (i < n1 && j < n2) {
+			if (L[i] <= R[j]) {
+				arr[k] = L[i];
+				i++;
+
+			}
+
+			else {
+				arr[k] = R[j];
+				count = count + (m + 1) - (l + i);
+				j++;
+
+			}
+			k++;
+		}
+
+		while (i < n1) {
+			arr[k] = L[i];
+			i++;
+			k++;
+		}
+
+		while (j < n2) {
+			arr[k] = R[j];
+			j++;
+			k++;
+		}
+		return count;
+
+	}
+
+}

Algorithms/MaximumSubarrayProblem.java

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+import java.util.*;
+
+public class MaximumSubarrayProblem {
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		System.out.println("Enter the no. of elements : ");
+		int n = sc.nextInt();
+
+		System.out.println("Enter " + n + " integers");
+		int[] numbers = new int[n];
+		for (int i = 0; i < n; i++) {
+
+			numbers[i] = sc.nextInt();
+		}
+		System.out.println("Given Array is ");
+		printArray(numbers);
+
+		int maxSum = maximumSubArraySum(numbers, 0, n - 1);
+		System.out.println("Maximum SubArray Sum is : " + maxSum);
+
+	}
+
+	static void printArray(int arr[]) {
+		int n = arr.length;
+		for (int i = 0; i < n; ++i)
+			System.out.print(arr[i] + " ");
+		System.out.println();
+	}
+
+	static int maximumSubArraySum(int[] arr, int l, int h) {
+		if (l == h) {
+			return arr[l];
+		}
+
+		int m = (l + h) / 2;
+
+		return Math.max(maximumCrossingSum(arr, l, m, h),
+				Math.max(maximumSubArraySum(arr, l, m), maximumSubArraySum(arr, m + 1, h)));
+	}
+
+	static int maximumCrossingSum(int[] arr, int l, int m, int h) {
+		double negInf = Double.NEGATIVE_INFINITY;
+		int sum = 0;
+		int rightSum = (int) negInf;
+		int leftSum = (int) negInf;
+		for (int i = m; i >= l; i--) {
+			sum = sum + arr[i];
+			if (sum > leftSum)
+				leftSum = sum;
+		}
+		sum = 0;
+		for (int i = m + 1; i <= h; i++) {
+			sum = sum + arr[i];
+			if (sum > rightSum)
+				rightSum = sum;
+		}
+		return Math.max(leftSum + rightSum, Math.max(leftSum, rightSum));
+
+	}
+}