打印一个句子中出现的所有单词恰好 K 次

给定一个由小写字母和整数K组成的字符串S ，任务是打印字符串S中出现K次的所有单词。

例子：

Input: S = “banana is in yellow and sun flower is also in yellow”, K = 2
Output: “is” “yellow” “in”
Explanation: The words “is”, “yellow” and “in” occurs in the string twice. 

Input: S = “geeks for geeks”, K = 2
Output: “geeks”

处理方法：按照以下步骤解决问题：

• 初始化一个列表l来存储字符串出现的单词。
• 拆分单词并将其存储在列表中。
• 遍历列表和每个单词：
  • 如果发现单词的频率为K ：
    • 打印那个词。
    • 从列表中删除该单词的当前出现。

下面是上述方法的实现：

C++

// CPP program for the above approach
#include
using namespace std;
 
// Function to print all the words
// occurring k times in a string
void kFreqWords(string S, int K)
{
 
  // Stores the words
  string temp = "";
  vector l;
  for (auto x: S)
  {
    if(x == ' ')
    {
      l.push_back(temp);
      temp = "";
    }
    else
      temp += x;
  }
 
  // Traverse the list
  for (auto x: l)
  {
 
    // Check for count
    if (count(l.begin(), l.end(), x) == K)
    {
 
      // Print the word
      cout << x << endl;
 
      // Remove from list
      remove(l.begin(),l.end(), x);
    }
  }
}
 
// Driver Code
int main()
{
 
  // Given string
  string S = "banana is in yellow and sun flower is also in yellow ";
 
  // Given value of K
  int K = 2;
 
  // Function call to find
  // all words occuring K times
  kFreqWords(S, K);
 
}
 
// This code is contributed by SURENDRA_GANGWAR.

Python3

# Python3 program for the above approach
 
# Function to print all the words
# occurring k times in a string
 
 
def kFreqWords(S, K):
 
    # Stores the words
    l = list(S.split(" "))
 
    # Traverse the list
    for i in l:
 
        # Check for count
        if l.count(i) == K:
 
            # Print the word
            print(i)
 
            # Remove from list
            l.remove(i)
 
 
# Driver Code
if __name__ == "__main__":
 
    # Given string
    S = "banana is in yellow and sun flower is also in yellow"
 
    # Given value of K
    K = 2
 
    # Function call to find
    # all words occuring K times
    kFreqWords(S, K)

输出

is
yellow
in

时间复杂度： O(N)
辅助空间： O(1)

方法#2：使用内置的Python函数：

• 因为句子中的所有单词都用空格分隔。
• 我们必须使用 split() 将句子按空格分割。
• 我们用空格分割所有单词并将它们存储在一个列表中。
• 使用计数器函数来计算单词的频率
• 遍历频率字典并打印频率为k的单词

下面是上述方法的实现：

蟒蛇3

# Python program for the above approach
from collections import Counter
 
# Python program to print words
# which occures k times
def printWords(sentence, k):
 
    # splitting the string
    lis = list(sentence.split(" "))
 
    # Calculating frequency of every word
    frequency = Counter(lis)
 
    # Traversing the frequency
    for i in frequency:
 
        # checking if frequency is k
 
        if(frequency[i] == k):
           
            # print the word
            print(i, end=" ")
 
 
# Driver code
# Given string
sentence = "sky is blue and my favourite color is blue"
 
# Given value of K
K = 2
 
printWords(sentence, K)
# this code is contributed by vikkycirus

输出：

is blue 

时间复杂度： O(N)

空间复杂度： O(N)

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