Question

我正在阅读未分类数字的文本文件

static void insertInOrder( int[] arr, int cnt, int newVal )
    {
        int belongs = -( bSearch( arr, 0, arr.length-1, newVal)) - 1;
        {
            for ( int i = cnt; i >= belongs+1 ; --i)
            {
                arr[i] = arr[i-1];
            }

        arr[belongs] = newVal;
    }

    }

    // We do not need to pass in count. The incoming lo and hi define the range
    public static int bSearch(int[] a, int lo, int hi, int key)
    {
    int mid = (lo+hi)/2;
    if(lo>hi)
        return -1;
    else if (a[mid]==key)
        return mid;
    else if (a[mid]<key)
        return bSearch(a, mid+1, hi, key);
    else
        return bSearch(a, lo, mid-1, key);
    }

二进制搜索正在运行，但我的insertinorder没有按升序排列数字，我无法弄清楚原因。它只是向后打印列表。这必须使用insertinorder中的递归二进制搜索来完成。

Answer 1

您是否已将最新代码复制到问题???中。

一个明显的问题是：

int belongs = -( bSearch( arr, 0, arr.length-1, newVal)) - 1;

方法 bSearch 在数组中找不到值时返回-1。当找不到newValue时，这将给出-2的插入点。您需要更改 bSearch 以返回找到的项目和位置。两个选项

创建（并返回）新类

private class FoundResult {
    boolean found = true;
    int position;
}

未找到时;返回-hi-1 即在bSearch中搜索一些东西：
```
if(lo>hi)
   return -hi-1;
```

对于选项1，代码将大致（我没有测试过）：

static void insertInOrder( int[] arr, int cnt, int newVal )     {

    int belongs = bSearch( arr, 0, arr.length-1, newVal)).position ;
    for ( int i = cnt; i >= belongs+1 ; --i) {
       arr[i] = arr[i-1];
    }

    arr[belongs] = newVal;
}

// We do not need to pass in count. The incoming lo and hi define the range
public static FoundResult bSearch(int[] a, int lo, int hi, int key)
{
int mid = (lo+hi)/2;
FoundResult ret;
if(lo>hi) {
    ret = new FoundResult();
    ret.found = false;
    ret.position = hi;
    return ret;
} else if (a[mid]==key) {
    ret = new FoundResult();
    ret.position = hi;
    return ret;
} else if (a[mid]<key) {
    return bSearch(a, mid+1, hi, key);
} else {
    return bSearch(a, lo, mid-1, key);
}

对于选项2，代码大致为：

static void insertInOrder( int[] arr, int cnt, int newVal )     {

    int belongs = bSearch( arr, 0, arr.length-1, newVal)) ;
    if (belongs < 0) {
        belongs  = -1 - belongs ;
    }
    for ( int i = cnt; i >= belongs+1 ; --i) {
       arr[i] = arr[i-1];
    }

    arr[belongs] = newVal;
}

// We do not need to pass in count. The incoming lo and hi define the range
public static int bSearch(int[] a, int lo, int hi, int key)
{
int mid = (lo+hi)/2;
FoundResult ret;
if(lo>hi) {
    return - hi - 1;
} else if (a[mid]==key) {
    return hi;
} else if (a[mid]<key) {
    return bSearch(a, mid+1, hi, key);
} else {
    return bSearch(a, lo, mid-1, key);
}

在InsertInOrder中使用递归二进制搜索

1 个答案: