Most frequent word in first String which is not present in second String

Given two string ‘S1’ and ‘S2’, the task is to return the most frequent (which is used the maximum number of times) word from ‘S1’ that is not present in ‘S2’. If more than one word is possible then print lexicographically smallest among them.


Input: S1 = “geeks for geeks is best place to learn”, S2 = “bad place”
Output: geeks
“geeks” is the most frequent word in S1 and is also not present in S2.

Input: S1 = “the quick brown fox jumps over the lazy dog”, S2 = “the brown fox jumps”
Output: dog


  • Iterate through string S2 and create a map and insert all of the words in it to the map.
  • Iterate through string S1 and check whether the word is not present in the map created in the previous step or not.
  • If the word satisfies the condition then update the answer if the frequency of the same word is maximum till now.
  • If the frequency of the word is equal to the previously chosen word then update the answer according to lexicographically smallest of the two strings.

Below is the implementation of above approach:






// CPP implementation of above approach
#include <bits/stdc++.h>
using namespace std;
// Function to return frequent
// word from S1 that isn't
// present in S2
string smallestFreq(string S1, string S2)
    map<string, int> banned;
    // create map of banned words
    for (int i = 0; i < S2.length(); ++i) {
        string s = "";
        while (i < S2.length() && S2[i] != ' ')
            s += S2[i++];
    map<string, int> result;
    string ans;
    int freq = 0;
    // find smallest and most frequent word
    for (int i = 0; i < S1.length(); ++i) {
        string s = "";
        while (i < S1.length() && S1[i] != ' ')
            s += S1[i++];
        // check if word is not banned
        if (banned[s] == 0) {
            if (result[s] > freq
                || (result[s] == freq && s < ans)) {
                ans = s;
                freq = result[s];
    // return answer
    return ans;
// Driver program
int main()
    string S1 = "geeks for geeks is best place to learn";
    string S2 = "bad place";
    cout << smallestFreq(S1, S2);
    return 0;



# Python3 implementation of above approach
from collections import defaultdict

# Function to return frequent
# word from S1 that isn’t
# present in S2
def smallestFreq(S1, S2):

banned = defaultdict(lambda:0)

i = 0

# create map of banned words
while i < len(S2): s = "" while i < len(S2) and S2[i] != ' ': s += S2[i] i += 1 i += 1 banned[s] += 1 result = defaultdict(lambda:0) ans = "" freq = 0 i = 0 # find smallest and most frequent word while i < len(S1): s = "" while i < len(S1) and S1[i] != ' ': s += S1[i] i += 1 i += 1 # check if word is not banned if banned[s] == 0: result[s] += 1 if (result[s] > freq or
(result[s] == freq and s < ans)): ans = s freq = result[s] # return answer return ans # Driver Code if __name__ == "__main__": S1 = "geeks for geeks is best place to learn" S2 = "bad place" print(smallestFreq(S1, S2)) # This code is contributed # by Rituraj Jain [tabbyending]



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Improved By : rituraj_jain