first-repeated-word-in-string.cpp

/*
Find the 1st repeated word in a string. (15 marks)
eg. Input: Ravi had been saying that he had been there
Output: had
*/

// CPP program for finding first repeated
// word in a string
#include <bits/stdc++.h>
using namespace std;

// returns first repeated word
string findFirstRepeated(string s){
	// break string into tokens
	// and then each string into set
	// if a word appeared before appears
	// again, return the word and break

	istringstream iss(s);
	string token;

	// hashmap for storing word and its count 
	// in sentence
	unordered_map<string,int> setOfWords;

	// store all the words of string
	// and the count of word in hashmap

    while (getline(iss, token, ' ')){
        if(setOfWords.find(token) != setOfWords.end()){
        	// word exist
        	setOfWords[token] += 1;
        }else{
        	// insert new word to set
        	setOfWords.insert(make_pair(token,1));
        }
    }

    // traverse again from first word of string s
    // to check if count of word is greater than 1
    istringstream iss2(s);
    while (getline(iss2, token, ' ')){
        int count = setOfWords[token];
        if(count > 1){
        	return token;
        }
    }

    return "NoRepetition";
}

// driver program
int main(){
	string s("Ravi had been saying that he had been there");
	string firstWord = findFirstRepeated(s);
	if(firstWord != "NoRepetition") 
		cout << "first repeated word :: " << firstWord << endl;
	else
		cout << "No Repetition\n";
	return 0;
}