# Find first undeleted integer from K to N in given unconnected Graph after performing Q queries

• Difficulty Level : Medium
• Last Updated : 09 Nov, 2021

Given a positive integer N representing the set of integers [1, N] and an array queries[] of length Q of type {L, K}, the task is to perform the given queries according to the following rules and print the result:

• If the value of L is 1, then delete the given integer K.
• If the value of L is 2, then print the first integer from K to N which is not deleted.

Note: When all the elements to the right are deleted, the answer will be -1.

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Examples:

Input: N = 3, queries[] = {{2, 1}, {1, 1}, {2, 1}, {2, 3}}
Output: 1 2 3
Explanation:
For the first query: the rightmost element for 1 is 1 only.
After the second query: 1 is deleted.
For the third query: the rightmost element for 1 is 2.
For the fourth query: the rightmost element for 3 is 3.

Input: N = 5, queries = {{2, 1}, {1, 3}, {2, 3}, {1, 2}, {2, 2}, {1, 5}, {2, 5}}
Output: 1 4 4 -1

Approach: The given problem can be solved by using Disjoint Set Union Data Structure. Initially, all the elements are in different sets, for the first type query perform the Union Operation on the given integer. For the second type of query, get the parent of the given vertex and print the value stored in the array graph[]. Follow the steps below to solve the problem:

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach`   `#include ` `using` `namespace` `std;`   `// Function to perform th Get operation` `// of disjoint set union` `int` `Get(vector<``int``>& graph, ``int` `a)` `{` `    ``return` `graph[a]` `           ``= (graph[a] == a ? a` `                            ``: Get(graph, graph[a]));` `}`   `// Function to perform the union` `// operation of disjoint set union` `void` `Union(vector<``int``>& graph,` `           ``int` `a, ``int` `b)` `{`   `    ``a = Get(graph, a);` `    ``b = Get(graph, b);`   `    ``// Update the graph[a] as b` `    ``graph[a] = b;` `}`   `// Function to perform given queries on` `// set of vertices initially not connected` `void` `Queries(vector >& queries,` `             ``int` `N, ``int` `M)` `{`   `    ``// Stores the vertices` `    ``vector<``int``> graph(N + 2);`   `    ``// Mark every vertices rightmost` `    ``// vertex as i` `    ``for` `(``int` `i = 1; i <= N + 1; i++) {`   `        ``graph[i] = i;` `    ``}`   `    ``// Traverse the queries array` `    ``for` `(``auto` `query : queries) {`   `        ``// Check if it is first type` `        ``// of the givan query` `        ``if` `(query.first == 1) {`   `            ``Union(graph, query.second,` `                  ``query.second + 1);` `        ``}` `        ``else` `{`   `            ``// Get the parent of a` `            ``int` `a = Get(graph, query.second);`   `            ``// Print the answer for` `            ``// the second query` `            ``if` `(a == N + 1)` `                ``cout << -1 << ``" "``;` `            ``else` `                ``cout << graph[a] << ``" "``;` `        ``}` `    ``}` `}`   `// Driver Code` `int` `main()` `{` `    ``int` `N = 5;` `    ``vector > queries{` `        ``{ 2, 1 }, { 1, 1 }, { 2, 1 }, { 2, 3 }` `    ``};` `    ``int` `Q = queries.size();`   `    ``Queries(queries, N, Q);`   `    ``return` `0;` `}`

## Java

 `// Java program for the above approach` `class` `GFG{`   `// Function to perform th Get operation` `// of disjoint set union` `public` `static` `int` `Get(``int``[] graph, ``int` `a)` `{` `    ``return` `graph[a]` `           ``= (graph[a] == a ? a` `                            ``: Get(graph, graph[a]));` `}`   `// Function to perform the union` `// operation of disjoint set union` `public` `static` `void` `Union(``int``[] graph,` `           ``int` `a, ``int` `b)` `{`   `    ``a = Get(graph, a);` `    ``b = Get(graph, b);`   `    ``// Update the graph[a] as b` `    ``graph[a] = b;` `}`   `// Function to perform given queries on` `// set of vertices initially not connected` `public` `static` `void` `Queries(``int``[][] queries,` `             ``int` `N, ``int` `M)` `{`   `    ``// Stores the vertices` `    ``int``[] graph = ``new` `int``[N + ``2``];`   `    ``// Mark every vertices rightmost` `    ``// vertex as i` `    ``for` `(``int` `i = ``1``; i <= N + ``1``; i++) {`   `        ``graph[i] = i;` `    ``}`   `    ``// Traverse the queries array` `    ``for` `(``int``[] query : queries) {`   `        ``// Check if it is first type` `        ``// of the givan query` `        ``if` `(query[``0``] == ``1``) {`   `            ``Union(graph, query[``1``],` `                  ``query[``1``] + ``1``);` `        ``}` `        ``else` `{`   `            ``// Get the parent of a` `            ``int` `a = Get(graph, query[``1``]);`   `            ``// Print the answer for` `            ``// the second query` `            ``if` `(a == N + ``1``)` `                ``System.out.print(-``1``);` `            ``else` `                ``System.out.print(graph[a] + ``" "``);` `        ``}` `    ``}` `}`   `// Driver Code` `public` `static` `void` `main(String args[])` `{` `    ``int` `N = ``5``;` `    ``int``[][] queries  = { { ``2``, ``1` `}, { ``1``, ``1` `}, { ``2``, ``1` `}, { ``2``, ``3` `}};` `    ``int` `Q = queries.length;`   `    ``Queries(queries, N, Q);`   `}` `}`   `// This code is contributed by gfgking.`

## Python3

 `# Python 3 program for the above approach`   `# Function to perform th Get operation` `# of disjoint set union` `def` `Get(graph, a):` `    ``if` `graph[graph[a]]!``=` `graph[a]:` `        ``graph[a] ``=` `Get(graph, graph[a])` `    ``else``:` `        ``return` `graph[a]`   `# Function to perform the union` `# operation of disjoint set union` `def` `Union(graph, a, b):` `    ``a ``=` `Get(graph, a)` `    ``b ``=` `Get(graph, b)`   `    ``# Update the graph[a] as b` `    ``graph[a] ``=` `b`   `# Function to perform given queries on` `# set of vertices initially not connected` `def` `Queries(queries, N, M):` `  `  `    ``# Stores the vertices` `    ``graph ``=` `[``0` `for` `i ``in` `range``(N ``+` `2``)]`   `    ``# Mark every vertices rightmost` `    ``# vertex as i` `    ``for` `i ``in` `range``(``1``,N ``+` `2``,``1``):` `        ``graph[i] ``=` `i`   `    ``# Traverse the queries array` `    ``for` `query ``in` `queries:` `      `  `        ``# Check if it is first type` `        ``# of the givan query` `        ``if` `(query[``0``] ``=``=` `1``):` `            ``Union(graph, query[``1``], query[``1``] ``+` `1``)`   `        ``else``:`   `            ``# Get the parent of a` `            ``a ``=` `Get(graph, query[``1``])`   `            ``# Print the answer for` `            ``# the second query` `            ``if` `(a ``=``=` `N ``+` `1``):` `                ``print``(``-``1``)` `            ``else``:` `                ``print``(graph[a],end ``=` `" "``)`   `# Driver Code` `if` `__name__ ``=``=` `'__main__'``:` `    ``N ``=` `5` `    ``queries ``=` `[[``2``, ``1``],[``1``, ``1``],[``2``, ``1``],[``2``, ``3``]]` `    ``Q ``=` `len``(queries)`   `    ``Queries(queries, N, Q)` `    `  `    ``# This code is contributed by SURENDRA_GANGWAR.`

## Javascript

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Output:

`1 2 3`

Time Complexity: O(M*log N)
Auxiliary Space: O(N)

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