如何在二进制搜索中获得一个大的十进制数组

如何解决如何在二进制搜索中获得一个大的十进制数组

我目前正在尝试完成一个项目。这段代码只是我一直在使用的二进制搜索算法。这是我做过的第一个搜索算法，因为我是一名自学程序员，我需要一些关于如何使这个算法也起作用的建议。我使用 QT Creator 作为 IDE。

我的代码中没有任何错误。但是，当我运行代码时，答案总是“找不到匹配项”。我认为这与数组本身有关，因为我之前用 10 个整数对其进行了测试，并且工作得很好。

我知道我不太擅长解释这个，因为我的英语很差。但如果您有任何问题，请回复我。

用 C++ 编写的代码

#include <iostream>
  using namespace std;

float binarySearch(float arr[],int left,int right,float x)
{
  while (left <= right)
  {
    int mid = left + (right - left) / 2;

    if (arr[mid] == x)
    {
      return mid;
    }
    else if (arr[mid] < x)
    {
      left = mid + 1;
    }
    else
    {
      right = mid - 1;
    }
  }

  return -1;
}

int main()
{
  float num;
  float output;

  float myarr[100] = {44.64978683,44.62352548,44.5972165,44.57086043,44.54445783,44.51800925,44.49151522,44.46497629,44.43839299,44.41176587,44.38509546,44.35838228,44.33162687,44.30482976,44.27799146,44.25111251,44.22419342,44.1972347,44.17023688,44.14320046,44.11612596,44.08901388,44.06186473,44.03467901,44.00745722,43.98019985,43.95290742,43.9255804,43.89821929,43.87082457,43.84339674,43.81593628,43.78844366,43.76091937,43.73336389,43.70577768,43.67816122,43.65051497,43.62283941,43.595135,43.56740221,43.53964148,43.51185328,43.48403806,43.45619628,43.42832838,43.40043481,43.37251603,43.34457246,43.31660456,43.28861275,43.26059748,43.23255917,43.20449827,43.17641519,43.14831036,43.12018421,43.09203716,43.06386963,43.03568203,43.00747477,42.97924828,42.95100295,42.92273919,42.89445742,42.86615803,42.83784141,42.80950798,42.78115811,42.75279222,42.72441067,42.69601387,42.6676022,42.63917604,42.61073577,42.58228177,42.55381441,42.52533407,42.49684112,42.46833593,42.43981886,42.41129027,42.38275054,42.35420001,42.32563904,42.29706799,42.26848721,42.23989705,42.21129785,42.18268996,42.15407372,42.12544947,42.09681755,42.06817829,42.03953203,42.01087909,41.98221981,41.9535545,41.9248835,41.89620711};

  while(true)
  {
      cout << "Please enter an element to search" << endl;
      cin >> num;

      output = binarySearch(myarr,100,num);

      if (output == -1)
      {
        cout << "No Match Found" << endl;
      }
      else
      {
        cout << "Match found at position: " << output << endl;
      }
  }
}

解决方法

数组 myarr 的元素是按降序排列的，所以当当前元素大于目标而不是小于目标时，left 应该设置为 mid+1。

错误：

    else if (arr[mid] < x)

正确：

    else if (arr[mid] > x)

而且数组只有 100 个元素，所以初始的 right 应该是 99，而不是 100。

错误：

      output = binarySearch(myarr,100,num);

正确：

      output = binarySearch(myarr,99,num);