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FindMaxRecursion.java

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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]);

}

}