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题解地址
代码

cpp
java
python3
C#
ruby
swift
golang
scala
kotlin
rust
php
typescript
elixir
dart
racket
erlang

介绍Programming-Idioms
介绍rosettacode

题解地址

https://leetcode.cn/problems/counting-words-with-a-given-prefix/solutions/2050442/by-yhm138_-jlr3/

代码

//点击指定元素
document.querySelector("#__next > div > div > div > div > div > div > div > div.shadow-level1.dark\\:shadow-dark-level1.flex.w-full.min-w-0.flex-col.rounded-xl.lc-lg\\:max-w-\\[700px\\].bg-layer-1.dark\\:bg-dark-layer-1 > div.relative.flex.w-full.flex-col > div.flex.w-full.flex-col.gap-4.px-5.pt-4.pb-8 > div.break-words > div > div > div > div.flex.select-none.bg-layer-2.dark\\:bg-dark-layer-2 > div:nth-child(13)").click();

cpp

//C++
class Solution {
public:
    int prefixCount(vector<string>& words, string pref) {
        return std::count_if(words.begin(), 
                             words.end(),
                             [&](auto s) { return s.find(pref) == 0; }
                            );
    }
};

java

//java
class Solution {
    public int prefixCount(String[] words, String pref) {
        return (int) Arrays.stream(words)
            .filter(word -> word.startsWith(pref))
            .count();
    }
}

python3

class Solution:
    def prefixCount(self, words: List[str], pref: str) -> int:
        return len(list(filter(lambda x: x.startswith(pref), words)))

C#

//c#
using System.Linq;

public class Solution {
    public int PrefixCount(string[] words, string pref) {
        return words.Count(word => word.StartsWith(pref));
    }
}

ruby

# ruby


# @param {String[]} words
# @param {String} pref
# @return {Integer}
def prefix_count(words, pref)
    words.count { |word| word.start_with?(pref) }
end

swift

//swift
class Solution {
    func prefixCount(_ words: [String], _ pref: String) -> Int {
        return words.filter { $0.starts(with: pref) }.count
    }
}

golang

//golang
func prefixCount(words []string, pref string) int {
  return len(filter(words, func(word string) bool {
    return strings.HasPrefix(word, pref)
  }))
}

func filter(vs []string, f func(string) bool) []string {
  vsf := make([]string, 0)
  for _, v := range vs {
    if f(v) {
      vsf = append(vsf, v)
    }
  }
  return vsf
}

scala

//scala 

object Solution {
    def prefixCount(words: Array[String], pref: String): Int = {
        return words.count(_.startsWith(pref));
    }
}

kotlin

//kotlin


class Solution {
    fun prefixCount(words: Array<String>, pref: String): Int {
        return words.count { it.startsWith(pref) }
    }
}

rust

//rust

impl Solution {
    pub fn prefix_count(words: Vec<String>, pref: String) -> i32 {
        words.iter().filter(|word| word.starts_with(&pref)).count() as i32
    }
}

php

//php

class Solution {

    /**
     * @param String[] $words
     * @param String $pref
     * @return Integer
     */
    function prefixCount($words, $pref) {
        return count(array_filter($words, function($word) use ($pref) {
            return strpos($word, $pref) === 0;
        }));
    }
}

typescript

//typescript

function prefixCount(words: string[], pref: string): number {
    return words.filter(word => word.startsWith(pref)).length;
};

elixir

# elixir

defmodule Solution do
  @spec prefix_count(words :: [String.t], pref :: String.t) :: integer
  def prefix_count(words, pref) do
    Enum.count(words, fn(word) -> String.starts_with?(word, pref) end)
  end
end

dart

//dart

class Solution {
  int prefixCount(List<String> words, String pref) {
    return words.where((word) => word.startsWith(pref)).length;
  }
}

racket

(define/contract (prefix-count words pref)
  (-> (listof string?) string? exact-integer?)
    (displayln (format "(string-prefix?  \"apple\" \"app\")=~a"  (string-prefix?  "apple" "app")  ))
    (displayln (format "(string-prefix?  \"app\" \"apple\")=~a"  (string-prefix?  "app" "apple")  ))
    (count  (lambda (word) (string-prefix? word pref)) words)
  )

; 不是，你这chatgpt连string-prefix? 入参的顺序都不知道？？？

erlang

% -import(binary).
% -import(unicode).



my_prefix([], _) -> true;
my_prefix([Ch | Rest1], [Ch | Rest2]) ->
        my_prefix(Rest1, Rest2);
my_prefix(_, _) -> false.



-spec prefix_count(Words :: [unicode:unicode_binary()], Pref :: unicode:unicode_binary()) -> integer().
prefix_count(Words, Pref) ->
    length(lists:filter(fun(Word) -> 
                            my_prefix(unicode:characters_to_list(Pref),unicode:characters_to_list(Word))  
                        end, Words)).

  
% 注意这里字符串用unicode_binary表示。
% erlang中字符串相关的list of bytes,unicode_binary,utf8_binary,list of code points的解析看这个帖子 https://stackoverflow.com/questions/19211584/unicodecharacters-to-list-seems-doesnt-work-for-utf8-list
% 下面是草稿
% io:write( binary:longest_common_prefix([<<"erlang">>, <<"ergonomy">>]) ),