【LeetCode2180】[GoC++C#RubySwiftKotlinRustPHPTSRacketDartJavaElixirScalaErlang] 统计各位数字之和为偶数的整数个数

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golang

//我的问题是，Go支持函数式编程吗？
func countEven(num int) int {

    a := makeRange(1, num)

    evenCount := len(filter(a, func(num int) bool {

        numStr := strconv.Itoa(num)

        digits := strings.Split(numStr, "")

        mySum:=0

        for _,ele :=range digits{

            d, _ := strconv.Atoi(ele)

            mySum=mySum+d

        }

        return mySum%2 == 0

    }))

    return evenCount

}
func filter(src []int, p func(int) bool) []int {

	dst := []int{}

	for _, s := range src {

		if p(s) {

			dst = append(dst, s)

		}

	}

	return dst

}
func makeRange(min, max int) []int {

    a := make([]int, max-min+1)

    for i := range a {

        a[i] = min + i

    }

    return a

}

c++

//C++

class Solution {

public:

    int countEven(int num) {

        std::vector<int> range(num);

        std::iota(range.begin(), range.end(), 1);

        return std::count_if(range.begin(), range.end(), [](int x) {

            std::string str = std::to_string(x);

            return std::accumulate(str.begin(), str.end(), 0, [](int sum, char c) {

                return sum + (c - '0');

            }) % 2 == 0;

        });

    }

};

C#

//C#

using System;

using System.Linq;
public class Solution {

    public int CountEven(int num) {

         return Enumerable.Range(1, num).Count(x => x.ToString().Select(c => c - '0').Sum() % 2 == 0);

    }

}

ruby

# ruby
# @param {Integer} num

# @return {Integer}

def count_even(num)

  (1..num).count { |x| x.to_s.chars.map(&:to_i).sum % 2 == 0 }

end

swift

//swift
class Solution {

    func countEven(_ num: Int) -> Int {

        return (1...num).filter { x in

            x.description.map { Int(String($0))! }.reduce(0, +) % 2 == 0

        }.count

    }

}

kotlin

//kotlin
class Solution {

    fun countEven(num: Int): Int {

        return (1..num).count {

            it.toString().toList().map { it.toInt() }.sum() % 2 == 0

        }

    }

}

rust

//rust
impl Solution {

    pub fn count_even(num: i32) -> i32 {

        (1..num+1).filter(|x| x.to_string().chars().map(|c| c.to_digit(10).unwrap()).sum::<u32>() % 2 == 0)

                  .count() as i32

    }

}

php

//php
class Solution {
/**

     * @param Integer $num

     * @return Integer

     */

    function countEven($num) {

        $result = array_filter(range(1, $num), function($x) {

            $sum = 0;

            foreach(str_split((string)$x) as $digit) {

                $sum += intval($digit);

            }

            return $sum % 2 == 0;

        });

        return count($result);

    }
}

typescript

//typescript
function countEven(num: number): number {

    return Array.from(Array(num).keys())

        .map(x => x + 1)

        .filter(x => x.toString()

            .split('')

            .map(Number)

            .reduce((a, b) => a + b, 0) % 2 === 0)

        .length;

}

racket

;racket
(define/contract (count-even num)

  (-> exact-integer? exact-integer?)

    (length

        (filter (lambda (x)

                (even? (apply + (map char->integer (string->list (number->string x))))))

            (range 1 (add1 num))

        )

    )

)

dart

//dart
class Solution {

  int countEven(int num) {

    return Iterable.generate(num, (x) => x+1)

        .where((x) =>

            x.toString().split('').map(int.parse).reduce((a,b) => a+b) % 2 == 0

        ).length;

    }

}

java

//java
import java.util.stream.IntStream;
public class Solution {

    public static int countEven(int num) {

        return (int) IntStream.range(1, num+1).filter(x ->

            IntStream.range(0, String.valueOf(x).length())

                .map(y -> Character.getNumericValue(String.valueOf(x).charAt(y)))

                .sum() % 2 == 0

        ).count();

    }

}

elixir

#elixir
defmodule Solution do

  @spec count_even(num :: integer) :: integer

  def count_even(num) do

    (1..num)|>

        Enum.count(fn x ->

             x |> Integer.to_string() |> String.graphemes() |> Enum.map(&String.to_integer/1) |> Enum.sum() |> rem(2) == 0

        end)

  end

end

scala

//scala
object Solution {

    def countEven(num: Int): Int = {

        Range(1,num+1,1).count(x=>{

            x.toString.toList.map(_.toInt).sum%2==0

        });

    }

}

erlang

%erlang
sum_digits(N) ->

    sum_digits(N, 0).
sum_digits(0, Sum) -> Sum;

sum_digits(N, Sum) ->

    sum_digits(N div 10, Sum + N rem 10).
-spec count_even(Num :: integer()) -> integer().

count_even(Num) ->

    lists:foldl(fun(X, Acc) ->

                    Sum = sum_digits(X),

                    if Sum rem 2 == 0 ->

                        Acc + 1;

                    true ->

                        Acc

                    end

                end,

    0,  [X || X <- lists:seq(1, Num)]).

说实话你用上FP就别指望什么性能了。。。

Rust一如既往的优秀哈， 0 ms 2 MB

如果要给{可读性，可维护性，代码长度，性能}排个序的话，应该是什么样的？

有些是拿适当的prompt问chatgpt写的。

有一些tips:

Range/rangeelixirfnendelixir

correct the erlang code

sum_digits(N) ->

    sum_digits(N, 0).
sum_digits(0, Sum) -> Sum;

sum_digits(N, Sum) ->

    sum_digits(N div 10, Sum + N rem 10).
-spec count_even(Num :: integer()) -> integer().

count_even(Num) ->

    lists:foldl(fun(X, Acc) ->

                    if sum_digits(X) rem 2 == 0 ->

                        Acc + 1;

                    true ->

                        Acc

                    end

                end,

    0,  [X || X <- lists:seq(1, Num)]).
Line 13: Char 24: call to local/imported function sum_digits/1 is illegal in guard

%   13|                     if sum_digits(X) rem 2 == 0 ->

%     |                        ^

)