Given an array of strings arr[], the task is to sort the array of strings according to frequency of each string, in ascending order. If two elements have same frequency, then they are sorted in lexicographical order.
Examples:
Input: arr[] = {“Geeks”, “for”, “Geeks”}
Output: {“for”, “Geeks”}
Explanation:
As string “Geeks” have frequency of 2 in the given array,
Hence the position of the string “Geeks” will be 2Input: arr[] = {“abc”, “pqr”, “pqr”, “abc”}
Output: {“abc”, “pqr”}
Explanation:
As both the strings have same frequency, the array is sorted in the lexicographical order.
Approach The idea is to use custom comparator to sort the array of strings with its frequency, as per the following steps.
- A map data structure is used to store the strings based on their frequency as (frequency, string) pairs.
- Sort these pairs with help of custom comparator such that if two strings have different frequency, the string with lower frequency is stored before. Otherwise if the frequency is same, then compare the strings lexicographically.
Below is the implementation of the above approach:
C++
// C++ implementation to sort the // array of strings by its frequency #include <bits/stdc++.h> using namespace std; // Custom comparator function to // sort the string by its frequency bool cmp(pair<int, string> x, pair<int, string> y) { // Condition to check if the // frequency of the string is less if (x.first < y.first) { return true; } // Condition to check if the // frequency of the string is greater else if (x.first > y.first) { return false; } // Condition when frequency of // the strings is equal else { // Condition to check if the // first string is lexicographically // smaller than second string if (x.second < y.second) { return true; } else { return false; } } } // Function to sort the array of strings // by its frequency in the array void printArraystring(string str[], int n) { unordered_map<string, int> m; // Loop to store the frequency // of a string in a hash-map for (int i = 0; i < n; i++) { m[str[i]]++; } // Iterator for the map vector<pair<int, string> > vec; // Loop to store the frequency and // string in a vector for (auto it = m.begin(); it != m.end(); it++) { vec.push_back( make_pair(it->second, it->first)); } // Sort the string // using custom comparator sort(vec.begin(), vec.end(), cmp); // Loop to print the sorted vector for (int i = 0; i < vec.size(); i++) { cout << vec[i].second << ", "; } } // Driver Code int main() { string arr[] = { "Geeks", "for", "Geeks", "for", "arc" }; int n = sizeof(arr) / sizeof(arr[0]); // Function to perform sorting printArraystring(arr, n); return 0; } |
Python 3
# Python 3 implementation to sort the # array of strings by its frequency # Custom comparator function to # sort the string by its frequency def srt(x): for i in range(len(x)-1): for j in range(i+1,len(x)): if(x[i][0]>x[j][0]): temp = x[j] x[j] = x[i] x[i] = temp elif(x[i][0] == x[j][0]): if(x[i][1]<x[j][1]): temp = x[j] x[j] = x[i] x[i] = temp # Function to sort the array of strings # by its frequency in the array def printArraystring(str,n): m = {str[i]:0 for i in range(n)} # Loop to store the frequency # of a string in a hash-map for i in range(n): m[str[i]] += 1 # Iterator for the map vec = [] # Loop to store the frequency and # string in a vector for key,value in m.items(): vec.append([value,key]) # Sort the string # using custom comparator srt(vec) # Loop to print the sorted vector for i in range(len(vec)): if i==len(vec)-1: print(vec[i][1]) else: print(vec[i][1],end = ",") # Driver Code if __name__ == '__main__': arr = ["Geeks", "for", "Geeks","for", "arc"] n = len(arr) # Function to perform sorting printArraystring(arr, n) # This code is contributed by Surendra_Gangwar |
arc, for, Geeks,
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
