Find the Smallest After Deleting Given Elements Using C++

In this problem, we are given two arrays arr[] and del[]. Our task is to find the smallest after deleting given elements.

We will be deleting values from the array arr[] that are present in del[]. And then print the smallest value after deletion.

Let’s take an example to understand the problem,

Input

arr[] = {2, 5, 6, 9, 1}
del[] = {1, 5, 9}

Output

2

Solution Approach

A simple solution to the problem is using hashing. We will insert all the values of del[] array in the hash table. Then we will traverse the array arr[] and check if the values in the hash table. If it is smaller than minVal. If yes, print minVal.

Example

Program to illustrate the working of our solution

#include <bits/stdc++.h>
using namespace std;
int findSmallestVal(int arr[], int m, int del[], int n){
   unordered_map<int, int> delVals;
   for (int i = 0; i < n; ++i) {
      delVals[del[i]]++;
   }
   int minVal = INT_MAX;
   for (int i = 0; i < m; ++i) {
   if (delVals.find(arr[i]) != delVals.end()) {
      delVals[arr[i]]--;
      if (delVals[arr[i]] == 0)
         delVals.erase(arr[i]);
      }
      else
         minVal = min(minVal, arr[i]);
   }
   return minVal;
}
int main(){
   int array[] = { 5, 12, 33, 4, 56, 12, 20 };
   int m = sizeof(array) / sizeof(array[0]);
   int del[] = { 12, 4, 56, 5 };
   int n = sizeof(del) / sizeof(del[0]);
   cout<<"The smallest value after the deleting element is "<<findSmallestVal(array, m, del, n);
   return 0;
}

Output

The smallest value after the deleting element is 12