Lock and Key Problem Using HashMap

A list of different locks and another list of keys are given. Our task is to find the correct match of lock and key from the given list, and assign that key with the lock when it is correct.

In this approach we will traverse all of the locks and create a hash-map, after that, each key is searched in the hash-map. When the key is matches, then that is marked as a valid key and assigned with a lock.

Input and Output

Input:
The lists of locks and keys.
lock = { ),@,*,^,(,%, !,$,&,#}
key = { !, (, #, %, ), ^, &, *, $, @ }
Output:
After matching Locks and Keys:
Locks: ! ( # % ) ^ & * $ @
Keys: ! ( # % ) ^ & * $ @

Algorithm

lockAndKeyProblem(lock, key, n)

Input: The list of locks, the list of keys, n.

Output: Find which key is for which lock.

Begin
   define hashmap
   for i in range (0 to n-1), do
      hashmap[lock[i]] := i  //set hashmap for locks
   done

   for i in range (0 to n-1), do
      if key[i] is found in the hashmap, then
         lock[i] = key[i]
   done
End

Example

#include<iostream>
#include<map>
using namespace std;

void show(char array[], int n) {
   for(int i = 0; i<n; i++)
      cout << array[i] << " ";
}

void lockAndKeyProblem(char lock[], char key[], int n) {
   map<char, int> hashMap;
   for(int i = 0; i<n; i++)
      hashMap[lock[i]] = i;           //hash map for locks

   for(int i = 0; i<n; i++) //for each keys for each lock
      if(hashMap.find(key[i]) != hashMap.end()) {
         lock[i] = key[i];
      }
}

int main() {
   char lock[] = {')','@','*','^','(','%','!','$','&','#'};
   char key[] = {'!','(','#','%',')','^','&','*','$','@'};
   int n = 10;
   lockAndKeyProblem(lock, key, n);
   cout << "After matching Locks and Keys:"<<endl;
   cout << "Locks: "; show(lock, n); cout << endl;
   cout << "Keys: "; show(key, n); cout << endl;
}

Output

After matching Locks and Keys:
Locks: ! ( # % ) ^ & * $ @
Keys: ! ( # % ) ^ & * $ @