我的代码在 C# 中搜索数组元素时遇到问题

Question

我一直在为这段代码苦苦挣扎，我似乎无法找出哪里出错了。基本上我想使用整数搜索一个数组，如果它匹配该数组中的一个元素，它会返回一个布尔变量为真。这是不言自明的，但我一生都无法弄清楚！有什么想法吗？

这里是代码；

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ArrayProject
{
    class ArrayProgram
    {
        public bool ElementAt(int[] intArray, int valueToBeFound)
        {
            bool intAt = false;
            int numberTofind;

            Console.WriteLine("Please enter the number you wish to search for within the array: ");
            numberTofind = Convert.ToInt32(Console.ReadLine());


            foreach (int x in intArray)
            {
                if (x == numberTofind)
                {
                    intAt = true;
                }
                else
                {
                    intAt = false;
                }
            }
            if (intAt == true)
            {
                Console.WriteLine("{0} is in the array!", numberTofind);
            }
            else
            {
                Console.WriteLine("{0} is not in the array.", numberTofind);
            }

            return intAt;
        }
        public void RunProgram()
        {
            int[] intArray = { 20, 30, 40, 50, 60, 50, 40, 30, 20, 10 };
            int numberTofind = 0;

            ElementAt(intArray, numberTofind);

        }  // end RunProgram()

        static void Main(string[] args)
        {
            ArrayProgram myArrayProgram = new ArrayProgram();
            myArrayProgram.RunProgram();

            Console.WriteLine("\n\n===============================");
            Console.WriteLine("ArrayProgram: Press any key to finish");
            Console.ReadKey();
        }
    }
}

Answer 1

        int[] intArray = { 20, 30, 40, 50, 60, 50, 40, 30, 20, 10 };
        int numberToFind = 0;

        //variant 1 (using System.Linq):
        bool bInside1 = intArray.Contains(numberToFind);

        //variant2
        bool bInside2 = Array.IndexOf(intArray, numberToFind) >= 0;

如果你想编写自己的函数：

    bool IsInside(int[] arrToSearch, int nToSearch)
    {
        foreach (int n in arrToSearch)
        {
            if (n == nToSearch)
                return true;
        }
        return false; //not found
    }

Answer 2

问题是您的循环会继续检查元素并更新intAt，即使它找到了您要查找的元素。

如果数组是{1, 2, 3, 4}，并且您的代码正在搜索1，它将首先检查索引0。这是一个匹配，所以intAt 变成了true。接下来它将尝试索引1。这个不匹配，所以它将intAt 设置为假。然后它将尝试索引2、3 等，但永远找不到匹配项。

Answer 3

您可以使用 Linq 轻松做到这一点。

using System.Linq;

public static string test(int[] numberArray, int find) 
{ 
            bool s = false;
            numberArray.ToList().ForEach(x => { if (x == find) s = true; }); 
            return s ? "It contains it." : "Can't find it.";
}

但是有一种方法可以做到这一点。正如我上面所说的那样，您可以将 .Contains 与数组一起使用。

Answer 4

如果你想保留你的实现，试试这个：

class ArrayProgram
{
    public bool ElementAt(int[] intArray, int valueToBeFound)
    {
        foreach (int x in intArray)     
            if (x == valueToBeFound)        // if you found your value in the array
                return true;                // you return true

        return false;   // otherwise, by this point the foreach has looped through all the elements and hasn't once entered in the above if (so it hasn't found your value) = you return false
    }

    public void RunProgram()
    {
        int[] intArray = { 20, 30, 40, 50, 60, 50, 40, 30, 20, 10,99 };
        int numberTofind;

        // I noticed that you're not using the numberTofind value either, so:

        Console.Write("Please enter the number you wish to search for within the array: ");
        numberTofind = Convert.ToInt32(Console.ReadLine());

        // and since you made a function that returns true if your value has been found, you might as well use it like this

        if(ElementAt(intArray, numberTofind)) // if the function returns true
            Console.WriteLine("{0} is in the array!", numberTofind);
        else
            Console.WriteLine("{0} is not in the array.", numberTofind);
    }  // end RunProgram()

    static void Main(string[] args)
    {
        ArrayProgram myArrayProgram = new ArrayProgram();
        myArrayProgram.RunProgram();

        Console.WriteLine("\n\n===============================");
        Console.WriteLine("ArrayProgram: Press any key to finish");
        Console.ReadKey();
    }
}