1.bfs.cpp

#include<bits/stdc++.h>

using namespace std;

int visited[1000];
int cost[1000];
vector <int> adj[1000];

void bfs(int s, int n)
{

    for (int i = 0; i < n; i++)
    {
        visited[i] = 0;
    }

    queue <int> Q;
    Q.push(s);
    visited[s] = 1;
    cost[s] = 0;
    while(!Q.empty())
    {
        int u = Q.front();
        Q.pop();

        for(int i = 0; i < adj[u].size(); i++ )
        {
            int  v = adj[u][i];
            if(visited[v] == 0)
            {
                visited[v] = 1;
                Q.push(v);
                cost[v] = cost[u] + 1;
            }
        }
    }

}
int main()
{
    int n, e;
    cout << "Enter nodes and edges" << endl;
    cin >> n >> e;
    for (int i = 1; i <= e; i++)
    {
        int x, y;
        cin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    cout << "source node\n";
    int s;
    cin >> s;
    bfs(s, n);
    int nn;
    cout << "Enter the measured node number\n";
    cin >> nn;
    cout << cost[nn];
    return 0;
}