55 lines
1.5 KiB
Java
55 lines
1.5 KiB
Java
package Maths;
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import java.util.Arrays;
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import java.util.Random;
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public class FindMaxRecursion {
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public static void main(String[] args) {
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Random rand = new Random();
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/* rand size */
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int size = rand.nextInt(100) + 1;
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int[] array = new int[size];
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/* init array with rand numbers */
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for (int i = 0; i < size; i++) {
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array[i] = rand.nextInt() % 100;
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}
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assert max(array, array.length) == Arrays.stream(array).max().getAsInt();
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assert max(array, 0, array.length - 1) == Arrays.stream(array).max().getAsInt();
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}
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/**
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* Get max of array using divide and conquer algorithm
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*
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* @param array contains elements
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* @param low the index of the first element
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* @param high the index of the last element
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* @return max of {@code array}
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*/
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public static int max(int[] array, int low, int high) {
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if (low == high) {
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return array[low]; //or array[high]
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}
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int mid = (low + high) >>> 1;
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int leftMax = max(array, low, mid); //get max in [low, mid]
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int rightMax = max(array, mid + 1, high); //get max in [mid+1, high]
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return Math.max(leftMax, rightMax);
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}
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/**
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* Get max of array using recursion algorithm
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*
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* @param array contains elements
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* @param len length of given array
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* @return max value of {@code array}
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*/
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public static int max(int[] array, int len) {
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return len == 1 ? array[0] : Math.max(max(array, len - 1), array[len - 1]);
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}
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}
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