查找

package com.kaibing.sortandfind;

import org.junit.jupiter.api.Test;

public class Find {


    public int[] arr = {1, 2, 3, 4, 5};


    @Test
    public void binaryFind() {
        System.out.println(binaryFindBody(0, arr.length - 1, arr, 58));
    }

    /**
     * 二分查找：基本思想是把数组分成两个分别查找
     * 时间：平均=O(log2n) | 最坏=O(log2n)
     * 空间：O(log2n)
     * 稳定性：稳定
     */
    public int binaryFindBody(int head, int tail, int[] arr, int find) {

        if (head > tail) {
            return -1;
        }

        int target = (head + tail) / 2;

        if (arr[target] == find) {
            return target;
        } else if (arr[target] > find && target > 0) {
            return binaryFindBody(head, target - 1, arr, find);
        } else {
            return binaryFindBody(target + 1, tail, arr, find);
        }
    }


}