简单的查找算法学习记录

简单的查找算法学习记录

package com.zhuguozhu.p1;

/**
 * 简单的查找算法实现
 * @author Guozhu Zhu
 * @date 2018/3/22
 * @version 1.0
 *
 */
public class SearchTest {
	
	public static void main(String[] args) {
		int[] arr = {1, 4, 6, 7, 8, 11};
		System.out.println(search01(arr, 4));
		System.out.println(search02(arr, 4));
		System.out.println(search03(arr, 4, 0, arr.length-1));
	}
	
    /*
     * 顺序查找
     */
	public static int search01(int[] arr, int e) {
		for (int i = 0; i < arr.length; i++) {
			if (e == arr[i]) {
				return i;
			}
		}
		return -1;
	}
	
	/*
	 * 二分查找
	 */
	public static int search02(int[] arr, int e) {
		int low = 0;
		int high = arr.length-1;
		int mid = 0;
		while (low <= high) {
			mid = (low + high) / 2;
			if (e < arr[mid]) {
				high = mid -1;
			} else if (e > arr[mid]) {
				low = mid + 1;
			} else {
				return mid;
			}
		}
		return -1;
	}
	
	/*
	 * 二分查找（递归实现)
	 */
	public static int search03(int[] arr, int e, int low, int high) {
		if (low > high) {
			return -1;
		}
		int mid = (low + high)/2;
		if (e == arr[mid] ){
			return mid;
		} else if (e < arr[mid]) {
			return search03(arr, e, low, mid-1);
		} else {
			return search03(arr, e, mid+1, high);
		}
	}

}