c# - 如何在二维数组中应用二进制搜索？

Question

我必须通过二进制搜索从数组中搜索姓名，但显示的是该人姓名的相应年龄。请不要提出其他建议，我必须使用二维数组的二进制搜索来完成。

string[,] persons = new string[4, 2];
persons[0, 0] = "Ana";
persons[0, 1] = "19";
persons[1, 0] = "Ammara";
persons[1, 1] = "20";
persons[2, 0] = "Marilyn";
persons[2, 1] = "40";
persons[3, 0] = "Zacharaia";
persons[3, 1] = "70";
string x = "Zacharia";
int upBound = persons.GetLength(0) - 1;
int lowBound = 0;
while (lowBound <= upBound)
{
    int midpoint = lowBound + (upBound - lowBound) / 2;
    int result = x.CompareTo(persons[midpoint, 1]);
    if (result == midpoint)
    {
        Console.WriteLine("The value is present at:" + persons[midpoint, 1]);
        break;
    }
    else if (result > midpoint)
    {
        lowBound = midpoint + 1;
        Console.WriteLine("The value is present at:" + persons[lowBound, 1]);
        break;
    }
    else if (result < midpoint)
    {
        upBound = midpoint - 1;
        Console.WriteLine("The value is present at:" + persons[upBound, 1]);
        break;
    }
}

此代码显示每个人的年龄为 20。CompareTo() 方法无效。

Answer 1

你的代码有 4 个主要问题:

1- 使用 midpoint2 , lowBound2和 upBound2由于不明原因，您应该使用 0和 1相反。

2- 由于您依赖二分查找，因此必须对关键元素进行排序，因此“Ana”必须在“Ammara”之后，尽管她更年轻，但您搜索的是名字而不是年龄，或者将其更改为另一个名字，例如“阿卡”。

3- result应该与 0 进行比较, < 0和 > 0 ，与midpoint无关.

4- 你应该使用 Console.WriteLine和 break在第一个条件下只让 while如果尚未找到该名称，则继续。

string[,] persons = new string[4, 2];
persons[0, 0] = "Aca";
persons[0, 1] = "19";
persons[1, 0] = "Ammara";
persons[1, 1] = "20";
persons[2, 0] = "Marilyn";
persons[2, 1] = "40";
persons[3, 0] = "Zach";
persons[3, 1] = "70";
string x = "Aca";
int upBound = persons.GetLength(0) - 1;
int lowBound = 0;
while (lowBound <= upBound)
{
    int midpoint = lowBound + (upBound - lowBound) / 2;
    int result = x.CompareTo(persons[midpoint, 0]);
    if (result == 0)
    {
        Console.WriteLine("The value is present at:" + persons[midpoint, 1]);
        break;
    }
    else if (result > 0)
    {
        lowBound = midpoint + 1;
    }
    else
    {
        upBound = midpoint - 1;
    }
}