Question

我有一个数组，由一个英文字母a到z组成，除了一个字母。我不知道缺少哪个元素，我只需要使用一个循环就可以找到该元素。我不能使用if语句和内置函数。

真的有可能吗？我在考试中遇到了这个问题，找不到任何解决方案，它的确使我吃不消。任何见解都很感激。

// missing 'h'
var letters = ['a','b','c','d','e','f','g','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];

for (var i = 0; i < letters.length; i++) {
 // find missing letter in 1 loop with no if statements or built-in functions 
}

Answer 1

这是代码：

             char[] inputs = { 'a', 'b', 'c', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };

             int total = 0;
             foreach (char c in inputs)
             {
                 total += (int)c - (int)'a';
             }
             char missingChar = (char)((int)('a') + (325 - total));

             // version 2
             total = 0;
             //from sum of a arithmetic sequence for even number of values
             // for example 1 + 2 + 3 + 4 = (1 + 4) + (2 + 3) = 2 * 5 = 10
             int expectedTotal = 13 * ((int)'a' + (int)'z');
             foreach (char c in inputs)
             {
                total += (int)c;
             }
             missingChar = (char)((expectedTotal - total));

Answer 2

 class Program
{
    private static void FindLetter(string[] alphabet, string[] yourMissingLetter)
    {
        for (var i = 0; i < yourMissingLetter.Length; i++)
        {
            var isit = alphabet[i] == yourMissingLetter[i];
            Console.WriteLine("alphabet[{0}] = {1}", alphabet[i], isit);
        } 
    }
    static void Main(string[] args)
    {
        string[] alphabet = { "A", "B", "C", "D" };
        // let's say your array is missing B
        string[] yourMissingLetterArray = { "A", "C", "D" };
        FindLetter(alphabet, yourMissingLetterArray);
    }
}

不如实际答案那么妙，但这将起作用：

当它开始丢失字母的那一刻，它将变为假，索引将向您显示它是哪个字母。

Answer 3

这是不使用任何循环而仅列出函数（控制台应用程序）的另一种方法，它还解决了小写比较问题：

namespace MissingAlphbetLetters
{
    class Program
    {

        public static List<char>  CheckDifferences(char[] str)
        {
            List<char> alphabet= new List<char>(new char[]
            { 'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'});
            List<char> compaired = str.ToList().ConvertAll(l => char.ToLower(l));
            List<char> difference = new List<char>();
            if (str.Length > 0)
            {
                difference = alphabet.Except(compaired).ToList();
            }
            return difference;
        }


        static void Main(string[] args)
        {
            Console.Write(string.Join(",",CheckDifferences(new char[]     { 'A', 'g', 't', 'h', 'o', 'm', 'd', 'e' })));
            Console.ReadLine();
        }
    }
}

查找数组中缺少的元素

3 个答案: