Why Graphs Exist and What Trees Cannot Model in DSA C - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a graph adjacency list in C.

DSA C

int [1][MAX_NODES][MAX_NODES];

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Atree

Bgraph

CadjacencyList

DadjacencyMatrix

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'tree' as the variable name which is misleading.

Using a 1D array instead of 2D for adjacency matrix.

The adjacency matrix is a 2D array representing edges between nodes in a graph.

2fill in blank

medium

Complete the code to add an edge between two nodes in an undirected graph.

DSA C

graph[u][v] = 1;
graph[[1]][[2]] = 1;

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Au

Bv

Cw

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same node 'u' for both indices in the second line.

Using an unrelated variable like 'w' or 'x'.

For undirected graphs, edges are bidirectional, so we mark both graph[u][v] and graph[v][u] as 1.

3fill in blank

hard

Fix the error in the code that tries to detect cycles in a graph using DFS.

DSA C

if (visited[[1]] && parent != [1]) {
    return 1;
}

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Anode

Bparent

Cneighbor

Dcurrent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'parent' inside visited[] which is incorrect.

Using 'current' instead of the neighbor node.

The condition checks if the neighbor is visited and is not the parent to detect a cycle.

4fill in blank

hard

Fill the blank to complete the function that prints all neighbors of a node in an adjacency matrix.

DSA C

for (int [1] = 0; [1] < numNodes; [1]++) {
    if (adjList[node][[1]] == 1) {
        printf("%d ", [1]);
    }
}

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AnumNodes

Bi

Cnode

Dj

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'node' or 'numNodes' as loop variables.

The loop variable 'i' is used to iterate over possible neighbors, check if adjList[node][i] == 1, and print i if connected.

5fill in blank

hard

Fill all three blanks to complete the code that initializes a graph with no edges.

DSA C

for (int [1] = 0; [1] < [2]; [1]++) {
    for (int [3] = 0; [3] < numNodes; [3]++) {
        graph[i][j] = 0;
    }
}

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Ai

BnumNodes

Cj

Dnode

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'node' as a loop variable which is confusing.

Using inconsistent variable names for loops.

We use 'i' and 'j' as loop variables and 'numNodes' as the limit to initialize all edges to 0.