13-02 Java Array Advanced algorithm, arrays class

Bubble sort

Bubble Sort Principle

Bubble Sort Code:

 Packagecn.itcast_01;/** Array sort of bubble sort: * Adjacent elements 22 comparison, large back, the first time, the maximum appears at the maximum index*/ Public classArraydemo { Public Static voidMain (string[] args) {//define an array        int[] arr = {24, 69, 80, 57, 13 }; System.out.println ("Before sorting:");        PrintArray (arr);        Bubblesort (arr); System.out.println ("After sorting:");    PrintArray (arr); }        //Bubble Sort Code    /*all you need to do is compare the array length-1 times, x < arr.length-1 * Each time the comparison is complete, the next one will reduce the element comparison. The first comparison has 0 elements that are no more than, the second time there are 1 elements not,,, so y < arr.length-1-X * 22 compared, big back put **/     Public Static voidBubblesort (int[] arr) {        for (int x = 0; x < arr.length-1; + +) {for (int y = 0; y < arr.length-1-X; y++) {                    if (Arr[y] > arr[y + 1]) {int temp = Arr[y];                    Arr[y] = arr[y + 1]; Arr[y + 1] = temp; }            }        }    }    //traversal function     Public Static voidPrintArray (int[] arr) {System.out.print ("[");  for(intx = 0; x < arr.length; X + +) {            if(x = = Arr.length-1) {System.out.print (arr[x]); } Else{System.out.print (arr[x]+ ", "); }} System.out.println ("]"); }}

Select sort

Select Sort schematic

Select Sort Code

 Packagecn.itcast_02;/** Sorting of arrays sorted by: * Starting with 0 index, comparing with subsequent elements, small forward, first completed, minimum value appears at the minimum index*/ Public classArraydemo { Public Static voidMain (string[] args) {//define an array        int[] arr = {24, 69, 80, 57, 13 }; System.out.println ("Before sorting:");                PrintArray (arr); //using methods to improveSelectsort (arr); System.out.println ("After sorting:");    PrintArray (arr); }    /** Array Sort **/     Public Static voidSelectsort (int[] arr) {        for (int x=0; x<arr.length-1; x + +) {for (int y=x+1; y<arr.length; y++) {if (Arr[y] <ar                    R[x]) {int temp = arr[x];                     ARR[X] = Arr[y]; Arr[y] = temp; }            }        }    }    //traversal function     Public Static voidPrintArray (int[] arr) {System.out.print ("[");  for(intx = 0; x < arr.length; X + +) {            if(x = = Arr.length-1) {System.out.print (arr[x]); } Else{System.out.print (arr[x]+ ", "); }} System.out.println ("]"); }}

Two-Part search method

Principle of Binary Search method

The code implementation of the dichotomy method:

 Packagecn.itcast_04;/** Find: * Basic find: Array elements unordered (find tail from scratch) * Binary lookup (binary lookup): array elements ordered * * Analysis: * A: Define maximum Index, minimum index * B:                 Calculate Intermediate Index * C: Compare the value of the intermediate index with the value to find * Equal: Returns the current intermediate index * Unequal: * Big left to find * Small right looking for * D: Recalculate Intermediate index * big left to find * max = mid-1; * Small Right to find * min = mid + 1; * E: Back to B*/ Public classArraydemo { Public Static voidMain (string[] args) {//define an array        int[] arr = {11,22,33,44,55,66,77}; //Write function Implementation        intindex = GetIndex (arr, 33); System.out.println ("Index:" +index); //What happens if this element does not exist?index = GetIndex (arr, 333); System.out.println ("Index:" +index); }        /** Two explicit: * return value type: int * parameter list: int[] arr,int value*/     Public Static intGetIndex (int[] arr,intvalue) {        //define maximum index, minimum index        intmax = Arr.length-1; intMin = 0; //Calculate the intermediate index        intMid = (max +min)/2; //Compare the value of the intermediate index with the value you want to find         while(Arr[mid]! =value) {            if(arr[mid]>value) {Max= Mid-1; }Else if(arr[mid]<value) {min= Mid + 1; }                        //Add judgment if (Min > Max) {return-1; } Mid= (max +min)/2; }                returnmid; }}

Arrays class

 Packagecn.itcast_05;Importjava.util.Arrays;/** Arrays: A tool class that operates on an array. such as sorting and finding. * 1:public static string toString (int[] a) turns the array into a string * 2:public static void sort (int[] a) sorts the arrays * 3:public static int bin Arysearch (int[] a,int key) Two-point lookup*/ Public classArraysdemo { Public Static voidMain (string[] args) {//define an array        int[] arr = {24, 69, 80, 57, 13 }; //Public static string toString (int[] a) turns the array into a stringSystem.out.println ("Before sorting:" +arrays.tostring (arr)); //Public static void sort (int[] a) sorting an arrayArrays.sort (arr); System.out.println ("After sorting:" +arrays.tostring (arr)); //[ +, +, +--]//public static int BinarySearch (int[] a,int key) Two-point lookupSystem.out.println ("BinarySearch:" + arrays.binarysearch (arr, 57)); System.out.println ("BinarySearch:" + arrays.binarysearch (arr, 577)); }}

13-02 Java Array Advanced algorithm, arrays class