package Maths;

import java.util.Arrays;
import java.util.Random;

public class FindMaxRecursion {
 public static void main(String[] args) {
 Random rand = new Random();

 /* rand size */
 int size = rand.nextInt(100) + 1;
 int[] array = new int[size];

 /* init array with rand numbers */
 for (int i = 0; i < size; i++) {
 array[i] = rand.nextInt() % 100;
 }

 assert max(array, array.length) == Arrays.stream(array).max().getAsInt();
 assert max(array, 0, array.length - 1) == Arrays.stream(array).max().getAsInt();
 }

 /**
 * Get max of array using divide and conquer algorithm
 *
 * @param array contains elements
 * @param low the index of the first element
 * @param high the index of the last element
 * @return max of {@code array}
 */
 public static int max(int[] array, int low, int high) {
 if (low == high) {
 return array[low]; //or array[high]
 }

 int mid = (low + high) >>> 1;

 int leftMax = max(array, low, mid); //get max in [low, mid]
 int rightMax = max(array, mid + 1, high); //get max in [mid+1, high]

 return Math.max(leftMax, rightMax);
 }

 /**
 * Get max of array using recursion algorithm
 *
 * @param array contains elements
 * @param len length of given array
 * @return max value of {@code array}
 */
 public static int max(int[] array, int len) {
 return len == 1 ? array[0] : Math.max(max(array, len - 1), array[len - 1]);
 }
}