排序

1 冒泡排序（不想多说）

public class BubbleSort {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int arr[]={1,6,0,-1,-100,90};
        int temp=0;
        for (int i = 0; i < arr.length-1; i++) {
            for (int j = 0; j < arr.length-i-1; j++) {
                if(arr[j]>arr[j+1]){
                    temp=arr[j];
                    arr[j]=arr[j+1];
                    arr[j+1]=temp;
                }
            }
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+" ");
        }
    }
}

2 简单选择排序（不想说）

public class Select_sort {
    public static void main(String[] args){
        int arr[]={8,3,2,1,7,11,6,5};
        int temp=0;
        for (int i = 0; i < arr.length-1; i++) {
            for (int j = i+1; j < arr.length; j++) {
                if(arr[j]<arr[i])
                {
                    temp=arr[i];
                    arr[i]=arr[j];
                    arr[j]=temp;
                }
            }
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+" ");
        }
    }
}

3 直接插入排序

public class InserSort {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int arr[]={23,15,-13,62,5,-23,0,17};
        for (int i = 1; i < arr.length; i++) {
            int insertVal=arr[i];
            int index=i-1;
            while(index>=0&&insertVal<arr[index]){
                arr[index+1]=arr[index];
                index--;
            }
            arr[index+1]=insertVal;
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+" ");
        }
    }
}

4 快速排序（只是参考，看我下一个严版的快排）http://www.cnblogs.com/clarencezzh/p/5117103.html

public class QuickSort {
    public void sort(int left,int right,int arr[]){
        int l=left;
        int r=right;
        int pivot=arr[(left+right)/2];
        int temp=0;
        while(l<r){
            while(arr[l]<pivot)l++;
            while(arr[r]>pivot)r--;
            if(l>=r)break;
            temp=arr[l];
            arr[l]=arr[r];
            arr[r]=temp;
            if(arr[l]==pivot)--r;
            if(arr[r]==pivot)++l;
        }
        if(l==r){
            l++;
            r--;
        }
        if(left<r) sort(left,r,arr);
        if(right>l) sort(l,right,arr);
    }
}

public class Test {
    public static void main(String[] args) {
        int arr[]={-1,-5,6,2,0,9,-3,-8,12,7};
        QuickSort quickSort=new QuickSort();
        quickSort.sort(0, arr.length-1, arr);
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
    }
}

5 二分查找

看王道上的书

class BinaryFind{
    public void find(int leftIndex,int rightIndex,int val,int arr[]){
        //首先找到中间的数
        int midIndex=((rightIndex+leftIndex)/2);
        int midVal=arr[midIndex];
        if(rightIndex>=leftIndex){
            //如果要找的数比midVal大
            if(midVal>val){
                //在arr数组左边数列中找
                find(leftIndex,midIndex-1,val,arr);
            }else if(midVal<val){
                //在arr数组右边数列中找
                find(midIndex+1,rightIndex,val,arr);
            }else if(midVal==val){
                System.out.println("数组arr["+midIndex+"]中的数字是"+arr[midIndex]);
            }
        }else{
            System.out.println("没有找到你要找的数!");
        }
    }
}

public class Test {
    public static void main(String[] args) {
        int arr[]={-1,-5,6,2,0,9,-3,-8,12,7};
        BinaryFind binaryFind=new BinaryFind();
        binaryFind.find(0, arr.length-1, 15, arr);
    }
}