Graph vs Tree Key Structural Difference in DSA C - Build Both Approaches

Graph vs Tree Key Structural Difference

📖 Scenario: Imagine you are organizing a family reunion and want to represent family relationships and friendships among relatives. You want to understand the difference between a family tree and a friendship network.

🎯 Goal: You will build simple data structures to represent a tree (family tree) and a graph (friendship network) and observe their key structural differences.

📋 What You'll Learn

Create an adjacency list for a tree with 5 nodes representing family members

Create an adjacency list for a graph with 5 nodes representing friendships

Add a variable to count edges in both structures

Implement a function to print adjacency lists

Print the adjacency lists to observe differences

💡 Why This Matters

🌍 Real World

Trees are used to represent hierarchical data like family trees or file systems, while graphs represent networks like social connections or roads.

💼 Career

Understanding trees and graphs is essential for software development, data analysis, and network design roles.

1

Create adjacency list for a tree

Create a 2D integer array called tree with size [5][3] to represent adjacency lists for each node. Initialize it with these edges: node 0 connected to 1 and 2, node 1 connected to 3, node 2 connected to 4. Use arrays of integers terminated by -1 for each adjacency list.

DSA C

// Your code here to create adjacency list for tree

Hint

Use a 2D array where each row holds connected nodes ending with -1.

2

Create adjacency list for a graph

Add a 2D integer array called graph with size [5][3] to represent adjacency lists for each node. Initialize it with these edges: node 0 connected to 1 and 2, node 1 connected to 0 and 3, node 2 connected to 0 and 4, node 3 connected to 1 and 4, node 4 connected to 2 and 3. Use arrays of integers terminated by -1 for each adjacency list.

DSA C

#include 

int tree[5][3] = {
    {1, 2, -1},
    {3, -1, -1},
    {4, -1, -1},
    {-1, -1, -1},
    {-1, -1, -1}
};

// Your code here to create adjacency list for graph

int main() {
    return 0;
}

Hint

Graph adjacency lists can have cycles, so nodes connect back and forth.

3

Add edge count variables

Add two integer variables: tree_edges set to 4, and graph_edges set to 5, representing the number of edges in the tree and graph respectively.

DSA C

#include 

int tree[5][3] = {
    {1, 2, -1},
    {3, -1, -1},
    {4, -1, -1},
    {-1, -1, -1},
    {-1, -1, -1}
};

int graph[5][3] = {
    {1, 2, -1},
    {0, 3, -1},
    {0, 4, -1},
    {1, 4, -1},
    {2, 3, -1}
};

// Your code here to add edge count variables

int main() {
    return 0;
}

Hint

Count edges manually based on connections in each structure.

4

Print adjacency lists

Write code to print the adjacency lists of tree and graph using a for loop with variable i from 0 to 4, and an inner for loop with variable j to print connected nodes until -1 is found. Print "Tree adjacency list:" before printing tree, and "Graph adjacency list:" before printing graph.

DSA C

#include 

int tree[5][3] = {
    {1, 2, -1},
    {3, -1, -1},
    {4, -1, -1},
    {-1, -1, -1},
    {-1, -1, -1}
};

int graph[5][3] = {
    {1, 2, -1},
    {0, 3, -1},
    {0, 4, -1},
    {1, 4, -1},
    {2, 3, -1}
};

int tree_edges = 4;
int graph_edges = 5;

// Your code here to print adjacency lists

int main() {
    return 0;
}

Hint

Use nested loops to print each node's connections until -1 is reached.