计算一个值在数组中出现的次数 [英] Counting the number of times a value appears in an array
问题描述
那么在 C# 中创建一个循环的好的简单算法是什么，每次某个值出现在数组中时，它都会将 1 添加到另一个数组中的计数器?
So what's a good, simple algorithm to create a loop in C# where every time a certain value appears in an array it adds 1 to a counter in another array?
例如我有这个:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication22
{
class Program
{
const int SIZE = 12;
static void Main(string[] args)
{
int[] numbers = new int[SIZE] {5, 5, 5, 7, 7, 7, 9, 7, 9, 9, 9, 1};
string[] letters = new string[SIZE] { "m", "m", "s", "m", "s", "s", "s", "m", "s", "s", "s", "s" };
int[] values = new int[SIZE] {15, 22, 67, 45, 12, 21, 24, 51, 90, 60, 50, 44};
string[] status = new string[SIZE] { "f", "m", "f", "a", "m", "f", "f", "f", "m", "f", "m", "f" };
int[] Count = new int[4];
int x = 0;
int i = 0;
for (i = 0; i < SIZE - 1; i++)
{
if (numbers[i] > 0 && numbers[i] < SIZE)
{
x = Count[i];
Count[x]++;
}
}
for (i = 0; i < 4; i++)
{
Console.WriteLine("{0}", Count[4]);
}
}
}
}
我只计算数字数组中出现 4 个数字的次数.有人建议我在第一个循环中使用该方法，但它似乎不起作用并创建了索引超出数组范围的错误.我想显示每个数字(5、7、9 和 1)出现在 4 行中的次数.
I am only counting the number of times 4 numbers appear in the numbers array. Someone suggested I use the method in the first loop but it doesn't seem to be working and creates an error that the index is out of bounds in the array. I want to display the number of times each of those numbers(5, 7,9 and 1) appear in 4 rows.
不使用 LINQ 或任何其他奇特的东西，如字典或其他任何东西.
Without using LINQ or any other fancy thing like Dictionary or whatever.
推荐答案
由于此部分，您得到索引越界错误:
You're getting an index out of bounds error because of this section:
for (i = 0; i < SIZE - 1; i++)
{
if (numbers[i] > 0 && numbers[i] < SIZE)
{
x = Count[i];
请注意，当 Count 仅具有4 的大小.
Notice that you're iterating through 0 to SIZE - 1 (11) when Count only has a size of 4.
不过，您可以使用 LINQ 轻松完成此任务.
You can do this task pretty easily with LINQ though.
int[] numbers = new int[SIZE] { 5, 5, 5, 7, 7, 7, 9, 7, 9, 9, 9, 1 };
var count = numbers
.GroupBy(e => e)
.Where(e => e.Count() == 4)
.Select(e => e.First());
因此它按数字对数字进行分组，然后我们将列表细化为仅包含 4 组，然后选择每个组中的第一个以留下 int 的集合.
So it groups the numbers by their value, we then refine the list to only include groups of 4, then select the first of each to be left with a collection of ints.
这是一个非基于 LINQ 的解决方案，使用字典来存储数字计数.
Here is a non-LINQ based solution using a Dictionary to store the count of numbers.
int[] numbers = new int[SIZE] { 5, 5, 5, 7, 7, 7, 9, 7, 9, 9, 9, 1 };
var dictionary = new Dictionary<int, int>();
var numbersWithFour = new List<int>();
foreach (var number in numbers)
{
if (dictionary.ContainsKey(number))
dictionary[number]++;
else
dictionary.Add(number, 1);
}
foreach (var val in dictionary)
{
if (val.Value == 4)
{
numbersWithFour.Add(val.Key);
}
}
<小时>
对您的程序稍作修改即可获得一些结果.
With a little modification to your program you can get some results.
int[] numbers = new int[SIZE] { 5, 5, 5, 7, 7, 7, 9, 7, 9, 9, 9, 1 };
string[] letters = new string[SIZE] { "m", "m", "s", "m", "s", "s", "s", "m", "s", "s", "s", "s" };
int[] values = new int[SIZE] { 15, 22, 67, 45, 12, 21, 24, 51, 90, 60, 50, 44 };
string[] status = new string[SIZE] { "f", "m", "f", "a", "m", "f", "f", "f", "m", "f", "m", "f" };
// Set the size of Count to maximum value in numbers + 1
int[] Count = new int[9 + 1];
int x = 0;
int i = 0;
for (i = 0; i < SIZE - 1; i++)
{
if (numbers[i] > 0 && numbers[i] < SIZE)
{
// Use value from numbers as the index for Count and increment the count
Count[numbers[i]]++;
}
}
for (i = 0; i < Count.Length; i++)
{
// Check all values in Count, printing the ones where the count is 4
if (Count[i] == 4)
Console.WriteLine("{0}", i);
}
输出:
7
9
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