Java-例题篇-简单002

最新推荐文章于 2021-02-27 02:39:37 发布

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最新推荐文章于 2021-02-27 02:39:37 发布

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分类专栏： Java-00-例题

本文链接：https://blog.youkuaiyun.com/qq_42211249/article/details/83932191

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这篇博客介绍了Java中针对数组的一系列操作，包括排序数组后使用二分查找法寻找元素的下标，排序数组并插入新元素，数组的逆置，搜索数组中的最大值和最小值，合并两个数组，判断数组相等，以及删除数组中的指定元素，和查找元素返回其下标。这些基本操作是Java编程中常见的问题，对于理解和提升数组处理能力非常有帮助。

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1.排序数组并二分查找某个元素，返回下标

public static int fun(int[] array,int value) {
        int min = 0,max = array.length - 1,mid = (min + max) / 2;
        while(array[mid] != value) {
            if(array[mid] < value) {
                min = mid + 1;
            }else if (array[mid] > value){
                max = mid - 1;
            }
            mid = (min + max) / 2;
            if(min > max) {
                return -1;
            }
        }
        return mid;
    }
    public static void main(String[] args) {
        int[] array = {10,22,34,4,5,93,66,18,42,57};
        Arrays.sort(array);
        System.out.println(Arrays.toString(array));
        System.out.print("输入想要查找的元素：");
        Scanner scanner = new Scanner(System.in);
        int val = scanner.nextInt();
        int i = fun(array,val);
        System.out.println("该元素下标为："+i);
    }

2.排序数组并插入某个元素

public static int[] fun2(int[] array,int value){
        int[] array2 = new int[array.length+1];
        int index = array.length;
        for(int i = 0; i < array.length; i++){
            if(value < array[i]){
                index = i;
                break;
            }
        }
        for(int j = array.length; j >= 0; j--){
            if(j > index) {
                array2[j] = array[j - 1];
            }
            if(j == index){
                array2[index] = value;
            }
            if(j < index){
                array2[j] = array[j];
            }
        }
        System.out.println("插入元素的下标是：" + index);
        //System.out.print("插入后的数组是： ");
        //System.out.println(Arrays.toString(array));
        return array2;
    }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
        Arrays.sort(array);
        System.out.println(Arrays.toString(array));
        System.out.print("输入想要插入的元素：");
        Scanner scanner = new Scanner(System.in);
        int val = scanner.nextInt();
        int[] array2 = fun2(array,val);
        System.out.print("插入后的数组是： ");
        System.out.println(Arrays.toString(array2));
    }

3.逆置数组

public static int[] fun3(int[] array) {
        for(int i = 0;i < (array.length) / 2;i++){
          int j = array.length - 1 - i;
          int tmp = array[i];
          array[i] = array[j];
          array[j] = tmp;
        }
        return array;
    }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
        System.out.println(Arrays.toString(array));
        fun3(array);
        System.out.println(Arrays.toString(array));
    }

或者不用返回数组：

public static void fun3(int[] array) {
        for(int i = 0;i < (array.length) / 2;i++){
          int j = array.length - 1 - i;
          int tmp = array[i];
          array[i] = array[j];
          array[j] = tmp;
        }
        //return array;
    }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
        System.out.println(Arrays.toString(array));
        fun3(array);
        System.out.println(Arrays.toString(array));
    }

4.搜索数组中的最大最小元素

public static int funMax(int[] array) {
        int max = array[0];
        for(int i = 1;i < array.length;i++){
            if(array[i] > max){
                max = array[i];
            }
        }
        return max;
    }
    public static int funMin(int[] array) {
        int min = array[0];
        for(int i = 1;i < array.length;i++){
            if(array[i] < min){
                min = array[i];
            }
        }
        return min;
    }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
        System.out.println(Arrays.toString(array));
        int a = funMax(array);
        System.out.println("数组中的最大元素是："+a);
        int b = funMin(array);
        System.out.println("数组中的最小元素是："+b);
    }

5.合并两个数组

public static int[] fun5(int[] array,int[] array2) {
        int[] array3 = new int[array.length + array2.length];
        for(int i = 0;i < array3.length;i++){
            if(i < array.length){
                array3[i] = array[i];
            }
            else{
                array3[i] = array2[i - array.length];
            }
        }
        return array3;
    }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
        System.out.println(Arrays.toString(array));
        int[] array2 = new int[]{15,23,30,2,7,96,64,10,48,55};
        System.out.println(Arrays.toString(array2));
        int[] array3 = fun5(array,array2);
        System.out.println("合并后的数组为：");
        System.out.println(Arrays.toString(array3));
    }

6.判断两个数组是否相等

public static boolean fun6(int[] arr1,int[] arr2) {
        if(arr1.length! = arr2.length){
            return false;
        }
        if(arr1.length == arr2.length) {
            for (int i = 0; i < arr1.length; i++) {
                if(arr1[i] != arr2[i]){
                    return false;
                }
            }
            return true;
        }
        return false;
    }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
        System.out.print("数组1为：");
        System.out.println(Arrays.toString(array));
        int[] array2 = new int[]{15,23,30,2,7,96,64,10,48,55};
        System.out.print("数组2为：");
        System.out.println(Arrays.toString(array2));
        int[] array3 = new int[]{10,22,34,4,5,93,66,18,42,57};
        System.out.print("数组3为：");
        System.out.println(Arrays.toString(array3));
        System.out.print("数组1和数组2相等：");
        boolean flg = fun6(array,array2);
        System.out.println(flg);
        System.out.print("数组1和数组3相等：");
        boolean flg2 = fun6(array,array3);
        System.out.println(flg2);
        boolean flg3 = Arrays.equals(array,array2);
        System.out.println(flg3);
    }

7.删除数组指定元素

public static int[] fun7(int[] array,int value) {
       int[] array2 = new int[array.length - 1];
       int index = array.length;
       for(int i = 0; i <array.length; i++){
           if(value == array[i]){
               index = i;
               break;
           }
       }
       for(int j = 0; j <array.length - 1; j++){
           if(j < index){
               array2[j] = array[j];
           }
           if(j >= index) {
               array2[j] = array[j + 1];
           }
       }
       System.out.println("删除元素的下标是：" + index);
       return array2;
   }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
       // Arrays.sort(array);
        System.out.println(Arrays.toString(array));
        System.out.print("输入想要删除的元素：");
        Scanner scanner = new Scanner(System.in);
        int val = scanner.nextInt();
        int[] array2 = fun7(array,val);
        System.out.print("删除后的数组是： ");
        System.out.println(Arrays.toString(array2));
    }

8.从数组中查找元素，返回下标

public static int fun8(int[] array,int value) {
        int a = -1;
        for(int i = 0;i < array.length;i++){
            if(array[i] == value){
                a = i;
            }
        }
        return a;
    }
    public static void main(String[] args) {
        int[] array = new int[]{10,22,34,4,5,93,66,18,42,57};
        System.out.println(Arrays.toString(array));
        System.out.print("输入想要查找的元素：");
        Scanner scanner = new Scanner(System.in);
        int val = scanner.nextInt();
        int i = fun8(array,val);
        System.out.println("该元素下标为："+i);
    }