# Find the value mapped to a given composite key for every query

Given three arrays firstkey[], secondkey[] and value[] where elements firstkey[i] and secondkey[i] denotes a composite key and their value is value[i], the task is to answer Q queries, each having two elements which denotes the composite key, whose corresponding value needs to be printed.
Examples:

Input: firstkey[] = {4, 4, 5}
secondkey[] = {2, 1, 3}
value[] = {5, 3, 8}, Q = {(4, 1)}
Output:
Explanation:
The composite key is present at firstkey[1] (= 4) and secondkey[1] (= 1)
Therefore, the corresponding value is value[1] = 3
Input: firstkey[] = {3, 4, 3}
secondkey[] = {7, 1, 3}
value[] = {2, 3, 6}, Q = {(3, 3)}
Output:
Explanation:
The composite key is present at firstkey[2] (= 3) and secondkey[2] (= 3)
Therefore, the corresponding value is value[2] = 6

Approach: The idea is to use map where the key of the map is a pair of two integers in C++, tuple in python denoting the respective elements of firstkey[] and secondkey[] which is mapped to the corresponding value[] element. This enables us to answer every query in the O(1) time.
For Example:

```Given arrays be -
firstkey[] = {4, 4, 5}
secondkey[] = {7, 1, 3}
value[] = {5, 3, 8}

Iterating over the Array, the map thus
formed is {(4, 7): 5, (4, 1): 3, (5, 3): 8}
```

Below is the implementation of the above approach:

## C++

 `// C++ implementation to find the ` `// value of the given composite keys ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Function to find the composite ` `// key value for multiple queries ` `void` `findCompositeKey(``int` `firstkey[], ` `                      ``int` `secondkey[], ``int` `value[], ``int` `n, ` `                      ``vector > q) ` `{ ` `    ``// Map to store the composite ` `    ``// key with a value ` `    ``map, ``int``> M; ` ` `  `    ``// Iterate over the arrays ` `    ``// and generate the required ` `    ``// mappings ` `    ``for` `(``int` `i = 0; i < n; i++) { ` `        ``M.insert({ { firstkey[i], secondkey[i] }, ` `                   ``value[i] }); ` `    ``} ` ` `  `    ``// Loop to iterate over the ` `    ``// elements of the queries ` `    ``for` `(``auto` `i : q) { ` ` `  `        ``// Condition to check if there ` `        ``// is the composite key in map ` `        ``if` `(M.find({ i.first, ` `                     ``i.second }) ` `            ``!= M.end()) { ` `            ``cout << M[{ i.first, i.second }] ` `                 ``<< endl; ` `        ``} ` `        ``else` `{ ` `            ``cout << ``"Not Found"` `<< endl; ` `        ``} ` `    ``} ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``int` `firstkey[] = { 4, 4, 5 }; ` `    ``int` `secondkey[] = { 2, 1, 3 }; ` `    ``int` `value[] = { 5, 3, 8 }; ` `    ``int` `n = 3; ` `    ``vector > q = { { 4, 1 }, ` `                                  ``{ 5, 2 }, ` `                                  ``{ 5, 3 } }; ` ` `  `    ``findCompositeKey(firstkey, secondkey, ` `                     ``value, n, q); ` `    ``return` `0; ` `} `

## Java

 `// Java implementation to find the ` `// value of the given composite keys ` `import` `java.util.*; ` ` `  `class` `GFG{ ` ` `  `static` `class` `Pair ` `{ ` `    ``int` `first, second; ` ` `  `    ``Pair(``int` `first, ``int` `second) ` `    ``{ ` `        ``this``.first = first; ` `        ``this``.second = second; ` `    ``} ` ` `  `    ``@Override` `    ``public` `boolean` `equals(Object obj) ` `    ``{ ` `        ``if` `(obj == ``null``) ` `            ``return` `false``; ` `        ``if` `(!(obj ``instanceof` `Pair)) ` `            ``return` `false``; ` `        ``if` `(obj == ``this``) ` `            ``return` `true``; ` `             `  `        ``return` `(``this``.first == ((Pair)obj).first) && ` `               ``(``this``.second == ((Pair)obj).second); ` `    ``} ` ` `  `    ``@Override` `    ``public` `int` `hashCode() ` `    ``{ ` `        ``return` `this``.first + ``this``.second; ` `    ``} ` `} ` ` `  `// Function to find the composite ` `// key value for multiple queries ` `static` `void` `findCompositeKey(``int` `firstkey[], ` `                            ``int` `secondkey[],  ` `                            ``int` `value[], ``int` `n, ` `                            ``int``[][] q) ` `{ ` `     `  `    ``// Map to store the composite ` `    ``// key with a value ` `    ``Map M = ``new` `HashMap<>(); ` ` `  `    ``// Iterate over the arrays ` `    ``// and generate the required ` `    ``// mappings ` `    ``for``(``int` `i = ``0``; i < n; i++) ` `    ``{ ` `        ``M.put(``new` `Pair(firstkey[i],  ` `                      ``secondkey[i]),  ` `                          ``value[i]); ` `    ``} ` ` `  `    ``// Loop to iterate over the ` `    ``// elements of the queries ` `    ``for``(``int` `i = ``0``; i < q.length; i++) ` `    ``{ ` ` `  `        ``// Condition to check if there ` `        ``// is the composite key in map ` `        ``if` `(M.containsKey(``new` `Pair(q[i][``0``], ` `                                   ``q[i][``1``]))) ` `        ``{ ` `            ``System.out.println(M.get(``new` `Pair(q[i][``0``], ` `                                              ``q[i][``1``]))); ` `        ``} ` `        ``else`  `        ``{ ` `            ``System.out.println(``"Not Found"``); ` `        ``} ` `    ``} ` `} ` ` `  `// Driver code ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``int` `firstkey[] = { ``4``, ``4``, ``5` `}; ` `    ``int` `secondkey[] = { ``2``, ``1``, ``3` `}; ` `    ``int` `value[] = { ``5``, ``3``, ``8` `}; ` `    ``int` `n = ``3``; ` `     `  `    ``int``[][] q = { { ``4``, ``1` `}, ` `                  ``{ ``5``, ``2` `}, ` `                  ``{ ``5``, ``3` `} }; ` ` `  `    ``findCompositeKey(firstkey, secondkey, ` `                     ``value, n, q); ` `} ` `} ` ` `  `// This code is contributed by offbeat `

Output:

```3
8
```

My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Improved By : offbeat

Article Tags :
Practice Tags :

3

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.