递归二分查找列表：“不是语句”？如何？

如何解决递归二分查找列表：“不是语句”？如何？

正在处理一项任务，但我一直遇到错误。我不太擅长 Java，所以我不确定我做错了什么。作业要我评估递归二分查找，我在 binarySearch 方法中发现了错误；它说“列表 = {“1,2,5,7,9,15”};”是表达式的非法开始，而不是语句，并且 ';'即使显然有一个也是预期的。我不知道……我有点压力山大。

方法如下：

//recursive binary search
    public boolean binarySearch(int[] list,int target,int low,int high) {
        list ={"1,15"}; 
        target = 5;
        boolean result = binarySearch(list,target,list.length-1);

        executions++;
        int mid = (low + high) / 2;

        if(!result){
            System.out.println("Target not found -- bad search.");
        }else{
            System.out.println("Target found -- sucessful search!");
        }    
        if (list[mid] == target) {
            return true;
        } else {
            if (low > high) {
                return false;
            } else {
                comparisons++;
                if (list[mid] < target) {
                    return binarySearch(list,mid + 1,high);
                } else {
                    return binarySearch(list,low,mid - 1);
                }
            }

这里是完整的代码：

public class Problem2 {
    public static int executions = 0;
    public static int comparisons = 0;
    public static int[] numbers = new int[] {1,3,4,6,8,10,11,12,13,14,15,16,17,18,19,20};

    public static void main(String[] args) {
        System.out.println("2nd fibonacci number: " + fibonacci(2));
        System.out.println("Number of executions: " + executions);
        System.out.println("Number of comparisons: " + comparisons);
        executions = 0;
        comparisons = 0;
        System.out.println();

        System.out.println("Number of operations: " + executions);
        System.out.println("Number of comparisons: " + comparisons);
        executions = 0;
        comparisons = 0;
        System.out.println();

        System.out.println("Factorial of 7: " + nFactorial(7));
        System.out.println("Number of operations: " + executions);
        System.out.println("Number of comparisons: " + comparisons);
        executions = 0;
        comparisons = 0;
    }
    //recursive Nfactorial
    public static int nFactorial(int n) {
        comparisons++;
        if (n <= 1) {
            return 1;
        } else {
            executions++;
            return n * nFactorial(n - 1);
        }
    }

    //recursive fibonacci number
    public static int fibonacci(int n) {
        comparisons++;
        if (n == 0) {
            return 0;
        } else if (n == 1) {
            return 1;
        } else {
            executions++;
            return fibonacci(n - 1) + fibonacci (n - 2);
        }
    }
    //recursive binary search
    public boolean binarySearch(int[] list,mid - 1);
                }
            }
        }    
    }
}

如果可以，请帮忙。如果您发现其他任何错误，请告诉我。

解决方法

问题

list ={"1,2,5,7,9,15"};

以上是java中初始化int数组的无效语句

修复

使用作为输入传递的数组

注意

初始化数组的正确方法是new int[]{1,15};

一个可能的解决方案

boolean binarySearch(int[] arr,final int left,final int right,final int target) {
        if (left > right) {
            return false;
        }
        final int mid = left + (right - left) / 2;
        if (arr[mid] == target) { // if matched,return true
            return true;
        } else if (arr[mid] < target) { // if candidate is less,then more towards right. drag left towards right(i.e: mid + 1)
            return binarySearch(arr,mid + 1,right,target);
        } else { // else drag right towards left (i.e. mid - 1)
            return binarySearch(arr,left,mid - 1,target);
        }
    }

调用

从主方法调用二分查找方法，带参数

public static void main(String[] args) {
  binarySearch(numbers,numbers.length - 1,5); // to find 5
}