一些簡單的入門算法

package com.study.algorithm;

import java.util.Scanner;

public class BinarySearch {
    public static void main(String[] args) {
       /* System.out.println("請輸入排序數組:");
        int array[] = new int[10];

        Scanner sc = new Scanner(System.in);
        for (int i = 0; i < array.length; i++) {
            array[i] = sc.nextInt();
        }*/
        int[] array = new int[]{25, 84, 455, 885, 4459, 6215, 244, 443, 4457, 1440};
        int a = BinarySearch(array, 10);
        System.out.println("數字下標是:" + a);
    }

    /**
     * 二分法查找
     *
     * @param array int数组
     * @param item  要查找的数字
     * @return 如果找到返回对应的下标, 下标从1开始。否则返回0
     */
    private static int BinarySearch(int[] array, int item) {
        //arrayays.sort(arrayay);
        //BubbleSort(array);
        //quickSort(array,0,array.length-1);
        doarrayertSort(array);
        for (int i = 0; i < array.length; i++) {
            System.out.println(array[i]);
        }
        int low = 0;
        int high = array.length - 1;
        while (low <= high) {
            int mid = (low + high) / 2;
            if (item == array[mid]) {
                return mid;
            } else if (item < array[mid]) {
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        return 0;
    }

    /**
     * 選擇排序
     *
     * @param arrayay
     */
    private static void sort(int[] arrayay) {
        for (int i = 0; i < arrayay.length; i++) {
            for (int j = i + 1; j < arrayay.length; j++) {
                if (arrayay[i] > arrayay[j]) {
                    int temp = arrayay[i];
                    arrayay[i] = arrayay[j];
                    arrayay[j] = temp;
                }
            }
        }
    }

    /**
     * 冒泡排序
     *
     * @param array
     */
    private static void BubbleSort(int[] array) {
        for (int i = 0; i < array.length - 1; i++) {
            for (int j = 0; j < array.length - i - 1; j++) {
                //每次比较都会确定一个最小数，所以j < array.length-1-i
                if (array[j] > array[j + 1]) {
                    int temp = array[j];
                    array[j] = array[j + 1];
                    array[j + 1] = temp;
                }
            }
        }
    }

    /**
     * 快速排序
     *
     * @param arr
     */
    private static void quickSort(int[] arr,int low,int high) {
//        int low = 0;
//        int high = arr.length - 1;
        if(low>high){
            return;
        }
        int i, j, temp, t;
        i = low;
        j = high;
        //temp就是基准位
        temp = arr[low];

        while (i < j) {
            //先看右边，依次往左递减
            while (temp <= arr[j] && i < j) {
                j--;
            }
            //再看左边，依次往右递增
            while (temp >= arr[i] && i < j) {
                i++;
            }
            //如果满足条件则交换
            if (i < j) {
                t = arr[j];
                arr[j] = arr[i];
                arr[i] = t;
            }

        }
        //最后将基准为与i和j相等位置的数字交换
        arr[low] = arr[i];
        arr[i] = temp;
        //递归调用左半数组
        quickSort(arr, low, j - 1);
        //递归调用右半数组
        quickSort(arr, j + 1, high);
    }

    /**
     * 插入排序
     * @param array
     */
    private static void doarrayertSort(int[] array){
        for(int i=1; i<array.length; i++){
            for(int j=i; j>0; j--){
                if(array[j]<array[j-1]){
                    int temp = array[j-1];
                    array[j-1] = array[j];
                    array[j] = temp;
                }
            }
        }

    }
}