# Check whether a node is leaf node or not for multiple queries

Given a tree with N vertices numbered from 0 to N – 1 where 0 is the root node. The task is to check if a node is leaf node or not for multiple queries.

Examples:

```Input:
0
/   \
1      2
/  \
3    4
/
5
q[] = {0, 3, 4, 5}
Output:
No
Yes
No
Yes
From the graph, 2, 3 and 5 are the only leaf nodes.
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Store the degree of all the vertices in an array degree[]. For each edge from A to B, degree[A] and degree[B] are incremented by 1. Now every node which not a root node and it has a degree of 1 is a leaf node and all the other nodes are not.

Below is the implementation of the above approach:

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to calculate the degree of all the vertices ` `void` `init(``int` `degree[], vector > edges, ``int` `n) ` `{ ` `    ``// Initializing degree of all the vertices as 0 ` `    ``for` `(``int` `i = 0; i < n; i++) { ` `        ``degree[i] = 0; ` `    ``} ` ` `  `    ``// For each edge from A to B, degree[A] and degree[B] ` `    ``// are increased by 1 ` `    ``for` `(``int` `i = 0; i < edges.size(); i++) { ` `        ``degree[edges[i].first]++; ` `        ``degree[edges[i].second]++; ` `    ``} ` `} ` ` `  `// Function to perform the queries ` `void` `performQueries(vector > edges, ` `                    ``vector<``int``> q, ``int` `n) ` `{ ` `    ``// To store the of degree ` `    ``// of all the vertices ` `    ``int` `degree[n]; ` ` `  `    ``// Calculate the degree for all the vertices ` `    ``init(degree, edges, n); ` ` `  `    ``// For every query ` `    ``for` `(``int` `i = 0; i < q.size(); i++) { ` ` `  `        ``int` `node = q[i]; ` `        ``if` `(node == 0) { ` `            ``cout << ``"No\n"``; ` `            ``continue``; ` `        ``} ` `        ``// If the current node has 1 degree ` `        ``if` `(degree[node] == 1) ` `            ``cout << ``"Yes\n"``; ` `        ``else` `            ``cout << ``"No\n"``; ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` ` `  `    ``// Number of vertices ` `    ``int` `n = 6; ` ` `  `    ``// Edges of the tree ` `    ``vector > edges = { ` `        ``{ 0, 1 }, { 0, 2 }, { 1, 3 }, { 1, 4 }, { 4, 5 } ` `    ``}; ` ` `  `    ``// Queries ` `    ``vector<``int``> q = { 0, 3, 4, 5 }; ` ` `  `    ``// Perform the queries ` `    ``performQueries(edges, q, n); ` ` `  `    ``return` `0; ` `} `

 `// Java implementation of the approach ` `import` `java.util.*; ` ` `  `class` `GFG  ` `{ ` `static` `class` `pair ` `{  ` `    ``int` `first, second;  ` `    ``public` `pair(``int` `first, ``int` `second)  ` `    ``{  ` `        ``this``.first = first;  ` `        ``this``.second = second;  ` `    ``}  ` `}  ` ` `  `// Function to calculate the degree  ` `// of all the vertices ` `static` `void` `init(``int` `degree[], ` `                     ``pair[] edges, ``int` `n) ` `{ ` `    ``// Initializing degree of  ` `    ``// all the vertices as 0 ` `    ``for` `(``int` `i = ``0``; i < n; i++)  ` `    ``{ ` `        ``degree[i] = ``0``; ` `    ``} ` ` `  `    ``// For each edge from A to B,  ` `    ``// degree[A] and degree[B] ` `    ``// are increased by 1 ` `    ``for` `(``int` `i = ``0``; i < edges.length; i++)  ` `    ``{ ` `        ``degree[edges[i].first]++; ` `        ``degree[edges[i].second]++; ` `    ``} ` `} ` ` `  `// Function to perform the queries ` `static` `void` `performQueries(pair [] edges, ` `                           ``int` `[]q, ``int` `n) ` `{ ` `    ``// To store the of degree ` `    ``// of all the vertices ` `    ``int` `[]degree = ``new` `int``[n]; ` ` `  `    ``// Calculate the degree for all the vertices ` `    ``init(degree, edges, n); ` ` `  `    ``// For every query ` `    ``for` `(``int` `i = ``0``; i < q.length; i++) ` `    ``{ ` ` `  `        ``int` `node = q[i]; ` `        ``if` `(node == ``0``) ` `        ``{ ` `            ``System.out.println(``"No"``); ` `            ``continue``; ` `        ``} ` `         `  `        ``// If the current node has 1 degree ` `        ``if` `(degree[node] == ``1``) ` `            ``System.out.println(``"Yes"``); ` `        ``else` `            ``System.out.println(``"No"``); ` `    ``} ` `} ` ` `  `// Driver code ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``// Number of vertices ` `    ``int` `n = ``6``; ` ` `  `    ``// Edges of the tree ` `    ``pair[] edges = {``new` `pair(``0``, ``1``),  ` `                    ``new` `pair(``0``, ``2``), ` `                    ``new` `pair(``1``, ``3``),  ` `                    ``new` `pair(``1``, ``4``),  ` `                    ``new` `pair(``4``, ``5``)}; ` ` `  `    ``// Queries ` `    ``int` `[]q = { ``0``, ``3``, ``4``, ``5` `}; ` ` `  `    ``// Perform the queries ` `    ``performQueries(edges, q, n); ` `} ` `} ` ` `  `// This code is contributed by Rajput-Ji `

 `# Python3 implementation of the approach  ` ` `  `# Function to calculate the degree ` `# of all the vertices  ` `def` `init(degree, edges, n) :  ` ` `  `    ``# Initializing degree of ` `    ``# all the vertices as 0  ` `    ``for` `i ``in` `range``(n) : ` `        ``degree[i] ``=` `0``;  ` ` `  `    ``# For each edge from A to B,  ` `    ``# degree[A] and degree[B]  ` `    ``# are increased by 1  ` `    ``for` `i ``in` `range``(``len``(edges)) : ` `        ``degree[edges[i][``0``]] ``+``=` `1``;  ` `        ``degree[edges[i][``1``]] ``+``=` `1``;  ` ` `  `# Function to perform the queries  ` `def` `performQueries(edges, q, n) :  ` ` `  `    ``# To store the of degree  ` `    ``# of all the vertices  ` `    ``degree ``=` `[``0``] ``*` `n;  ` ` `  `    ``# Calculate the degree for all the vertices  ` `    ``init(degree, edges, n);  ` ` `  `    ``# For every query  ` `    ``for` `i ``in` `range``(``len``(q)) : ` ` `  `        ``node ``=` `q[i];  ` `        ``if` `(node ``=``=` `0``) : ` `            ``print``(``"No"``);  ` `            ``continue``;  ` ` `  `        ``# If the current node has 1 degree  ` `        ``if` `(degree[node] ``=``=` `1``) : ` `            ``print``(``"Yes"``);  ` `        ``else` `: ` `            ``print``(``"No"``);  ` ` `  `# Driver code  ` `if` `__name__ ``=``=` `"__main__"` `:  ` ` `  `    ``# Number of vertices  ` `    ``n ``=` `6``;  ` ` `  `    ``# Edges of the tree  ` `    ``edges ``=` `[[ ``0``, ``1` `], [ ``0``, ``2` `],  ` `             ``[ ``1``, ``3` `], [ ``1``, ``4` `],  ` `             ``[ ``4``, ``5` `]];  ` ` `  `    ``# Queries  ` `    ``q ``=` `[ ``0``, ``3``, ``4``, ``5` `];  ` ` `  `    ``# Perform the queries  ` `    ``performQueries(edges, q, n);  ` ` `  `# This code is contributed by AnkitRai01 `

 `// C# implementation of the approach ` `using` `System; ` `                     `  `class` `GFG  ` `{ ` `public` `class` `pair ` `{  ` `    ``public` `int` `first, second;  ` `    ``public` `pair(``int` `first, ``int` `second)  ` `    ``{  ` `        ``this``.first = first;  ` `        ``this``.second = second;  ` `    ``}  ` `}  ` ` `  `// Function to calculate the degree  ` `// of all the vertices ` `static` `void` `init(``int` `[]degree, ` `                 ``pair[] edges, ``int` `n) ` `{ ` `    ``// Initializing degree of  ` `    ``// all the vertices as 0 ` `    ``for` `(``int` `i = 0; i < n; i++)  ` `    ``{ ` `        ``degree[i] = 0; ` `    ``} ` ` `  `    ``// For each edge from A to B,  ` `    ``// degree[A] and degree[B] ` `    ``// are increased by 1 ` `    ``for` `(``int` `i = 0; i < edges.Length; i++)  ` `    ``{ ` `        ``degree[edges[i].first]++; ` `        ``degree[edges[i].second]++; ` `    ``} ` `} ` ` `  `// Function to perform the queries ` `static` `void` `performQueries(pair [] edges, ` `                            ``int` `[]q, ``int` `n) ` `{ ` `    ``// To store the of degree ` `    ``// of all the vertices ` `    ``int` `[]degree = ``new` `int``[n]; ` ` `  `    ``// Calculate the degree for all the vertices ` `    ``init(degree, edges, n); ` ` `  `    ``// For every query ` `    ``for` `(``int` `i = 0; i < q.Length; i++) ` `    ``{ ` ` `  `        ``int` `node = q[i]; ` `        ``if` `(node == 0) ` `        ``{ ` `            ``Console.WriteLine(``"No"``); ` `            ``continue``; ` `        ``} ` `         `  `        ``// If the current node has 1 degree ` `        ``if` `(degree[node] == 1) ` `            ``Console.WriteLine(``"Yes"``); ` `        ``else` `            ``Console.WriteLine(``"No"``); ` `    ``} ` `} ` ` `  `// Driver code ` `public` `static` `void` `Main(String[] args) ` `{ ` `    ``// Number of vertices ` `    ``int` `n = 6; ` ` `  `    ``// Edges of the tree ` `    ``pair[] edges = {``new` `pair(0, 1),  ` `                    ``new` `pair(0, 2), ` `                    ``new` `pair(1, 3),  ` `                    ``new` `pair(1, 4),  ` `                    ``new` `pair(4, 5)}; ` ` `  `    ``// Queries ` `    ``int` `[]q = { 0, 3, 4, 5 }; ` ` `  `    ``// Perform the queries ` `    ``performQueries(edges, q, n); ` `} ` `} ` ` `  `// This code is contributed by 29AjayKumar `

Output:
```No
Yes
No
Yes
```

Time complexity: O(n)

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Improved By : AnkitRai01, Rajput-Ji, 29AjayKumar

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