133. Clone Graph

Problem

Tags: Hash Table, Depth-First Search, Breadth-First Search, Graph

Given a reference of a node in a connected undirected graph.

Return a deep copy (clone) of the graph.

Each node in the graph contains a value (int) and a list (List[Node]) of its neighbors.

class Node {
    public int val;
    public List<Node> neighbors;
}

Test case format:

For simplicity, each node's value is the same as the node's index (1-indexed). For example, the first node with val == 1, the second node with val == 2, and so on. The graph is represented in the test case using an adjacency list.

An adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.

The given node will always be the first node with val = 1. You must return the copy of the given node as a reference to the cloned graph.

Example 1:

Input: adjList = [[2,4],[1,3],[2,4],[1,3]]
Output: [[2,4],[1,3],[2,4],[1,3]]
Explanation: There are 4 nodes in the graph.
1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).

Example 2:

Input: adjList = [[]]
Output: [[]]
Explanation: Note that the input contains one empty list. The graph consists of only one node with val = 1 and it does not have any neighbors.

Example 3:

Input: adjList = []
Output: []
Explanation: This an empty graph, it does not have any nodes.

Constraints:

• The number of nodes in the graph is in the range [0, 100].
• 1 <= Node.val <= 100
• Node.val is unique for each node.
• There are no repeated edges and no self-loops in the graph.
• The Graph is connected and all nodes can be visited starting from the given node.

Code

C

// 133. Clone Graph (1/18/54117)
// Runtime: 0 ms (93.59%) Memory: 6.78 MB (80.77%) 

/**
 * Definition for a Node.
 * struct Node {
 *     int val;
 *     int numNeighbors;
 *     struct Node** neighbors;
 * };
 */

struct Node* clone(struct Node* source, struct Node* created[]) {
    if (source == NULL) {
        return NULL;
    }

    if (!created[source->val]) {
        struct Node* cloned = (struct Node*)malloc(1 * sizeof(struct Node));
        cloned->val = source->val;
        cloned->numNeighbors = source->numNeighbors;
        cloned->neighbors = (struct Node**)malloc(source->numNeighbors * sizeof(struct Node*));

        created[source->val] = cloned;

        for (int i = 0; i < source->numNeighbors; i++) {
            cloned->neighbors[i] = clone(source->neighbors[i], created);
        }
    }

    return created[source->val];
}

struct Node* cloneGraph(struct Node* s) {
    struct Node* created[101] = { NULL };
    return clone(s, created);
}