Given a string str and a word w, the task is to print the number of the occurrence of the given word in the string str using Regular Expression.
Examples:
Input: str = “peter parker picked a peck of pickled peppers”, w = “peck”
Output: 1
Explanation: There is only one occurrence of the word “peck” in the given string. Therefore, the output is 1.
Input: str = “How much wood would a woodchuck chuck if a woodchuck could chuck wood ?”, w = “wood”
Output: 2
Explanation: There are only two occurrences of the word “wood” in the given string.
Therefore, the output is 2.Input: str = “She sells seashells by the seashore”, w = “sea”
Output: 0
Explanation: There is no occurrence of the word “sea” in the given string. Therefore, the output is 0.
Approach: The required regular expression to find the required count of string w in the given string is “\\bw\\b”, where \b is a word boundary. Follow the steps to solve the problem
- Create the regular expression pattern for the word w
regex = “\\bw\\b”
- Traverse the string, match the regex with the string str using regex_iterator(). Simultaneously, update number of matches.
- Print the total number of matches obtained in the above step.
Below is the implementation of the above approach :
C++
// C++ program for the above approach#include <iostream>#include <regex>using namespace std;// Function to count total occurrences// of word "w" in string "str"void countOccurrences(string str, string w){ // Get the regex to be checked string regexPattern = "\\b" + w + "\\b"; const regex pattern(regexPattern); // Variable to count total // occurrences of the given word int count = 0; auto it = sregex_iterator(str.begin(), str.end(), pattern); for (it; it != sregex_iterator(); it++) { // Increment count count++; } // Print the occurrences of the word cout << count << endl; return;}// Driver Codeint main(){ // Input string str = "peter parker picked a peck of pickled peppers"; string w = "peck"; countOccurrences(str, w); return 0;} |
Java
// Java program for the above approachimport java.util.*;import java.util.regex.*;class GFG { // Function to count total occurrences // of word "w" in String "str" static void countOccurrences(String str, String w) { // Get the regex to be checked String regexPattern = "\\b" + w + "\\b"; Pattern pattern = Pattern.compile(regexPattern); // Variable to count total // occurrences of the given word int count = 0; while (str.contains(w)) { str = str.replace(w, ""); // Increment count count++; } // Print the occurrences of the word System.out.print(count + "\n"); return; } // Driver Code public static void main(String[] args) { // Input String str = "peter parker picked a peck of pickled peppers"; String w = "peck"; countOccurrences(str, w); }}// This code is contributed by gauravrajput1 |
Python3
# Python program for the above approachimport re# Function to count total occurrences# of word "w" in String "str"def countOccurrences(str,w): # Get the regex to be checked regexPattern = "\\b" + w + "\\b" # Variable to count total # occurrences of the given word count=0 for m in re.finditer(regexPattern, str): # Increment count count=count+1 # Print the occurrences of the word print(count) # Driver Code# Inputstr = "peter parker picked a peck of pickled peppers"w = "peck"countOccurrences(str,w)# This code is contributed by Pushpesh Raj. |
C#
// C# program for the above approachusing System;using System.Text.RegularExpressions;public class GFG { // Function to count total occurrences // of word "w" in String "str" static void countOccurrences(String str, String w) { // Get the regex to be checked String regexPattern = "\\b" + w + "\\b"; Regex rx = new Regex(regexPattern,RegexOptions.Compiled | RegexOptions.IgnoreCase); // Variable to count total // occurrences of the given word int count = 0; while (str.Contains(w)) { str = str.Replace(w, ""); // Increment count count++; } // Print the occurrences of the word Console.Write(count + "\n"); return; } // Driver Code public static void Main(String[] args) { // Input String str = "peter parker picked a peck of pickled peppers"; String w = "peck"; countOccurrences(str, w); }}// This code is contributed by gauravrajput1 |
Javascript
//// Javascript program for the above approachfunction countOccurrences(string, substring) { var n = 0; var position = 0; while (true) { position = string.indexOf(substring, position); if (position != -1) { n++; position += substring.length; } else { break; } } return n;}console.log(countOccurrences("peter parker picked a peck of pickled peppers", "peck")); // This code is contributed By Rahul Chauhan |
1
Time Complexity : O(N)
Auxiliary Space : O(N)
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