BFS: Shortest Reach in a Graph

  • + 0 comments

    Consider an undirected graph consisting of nodes where each node is labeled from to and the edge between any two nodes is always of length . We define node to be the starting position for a BFS. Given a graph, determine the distances from the start node to each of its descendants and return the list in node number order, ascending. If a node is disconnected, it's distance should be .

    For example, there are nodes in the graph with a starting node . The list of , and each has a weight of .

    image

    Starting from node and creating a list of distances, for nodes through we have .

    Function Description

    Define a Graph class with the required methods to return a list of distances.

    Input Format

    The first line contains an integer, , the number of queries.

    Each of the following sets of lines is as follows:

    The first line contains two space-separated integers, and , the number of nodes and the number of edges. Each of the next lines contains two space-separated integers, and , describing an edge connecting node to node . The last line contains a single integer, , the index of the starting node. Constraints

    Output Format

    For each of the queries, print a single line of space-separated integers denoting the shortest distances to each of the other nodes from starting position . These distances should be listed sequentially by node number (i.e., ), but should not include node . If some node is unreachable from , print as the distance to that node.

    Sample Input

    2 4 2 1 2 1 3 1 3 1 2 3 2 Sample Output

    6 6 -1 -1 6 Explanation

    We perform the following two queries:

    The given graph can be represented as: image where our start node, , is node . The shortest distances from to the other nodes are one edge to node , one edge to node , and there is no connection to node . The given graph can be represented as: image where our start node, , is node . There is only one edge here, so node is unreachable from node and node has one edge connecting it to node . We then print node 's distance to nodes and (respectively) as a single line of space-separated integers: -1 6.

    Note: Recall that the actual length of each edge is , and we print as the distance to any node that's unreachable from .

    Language C++

    More 16171819202122910111213141583456712

    include

    include

    include

    include

    include

    using namespace std;

    class Graph { public: Graph(int n) {

    Line: 3 Col: 18

    Submit Code

    Run Code

    Upload Code as File

    Test against custom input BlogScoringEnvironment