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Convert an array to reduced form (Hashing) in C++
In this tutorial, we will be discussing a program to convert an array to its reduced form using hashing.
For this we will be provided with an array. Our task is to convert the given array in its reduced form such that it only contains elements ranging from 0 to n-1.
Example
#include <bits/stdc++.h> using namespace std; //converting array to its reduced form void convert(int arr[], int n){ // copying the elements of array int temp[n]; memcpy(temp, arr, n*sizeof(int)); sort(temp, temp + n); //creating a hash table unordered_map<int, int> umap; int val = 0; for (int i = 0; i < n; i++) umap[temp[i]] = val++; //putting values in the hash table for (int i = 0; i < n; i++) arr[i] = umap[arr[i]]; } void print_array(int arr[], int n) { for (int i=0; i<n; i++) cout << arr[i] << " "; } int main(){ int arr[] = {10, 20, 15, 12, 11, 50}; int n = sizeof(arr)/sizeof(arr[0]); cout << "Given Array :\n"; print_array(arr, n); convert(arr , n); cout << "\nConverted Array:\n"; print_array(arr, n); return 0; }
Output
Given Array : 10 20 15 12 11 50 Converted Array: 0 4 3 2 1 5
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