SQUARE ROOT OF A NUMBER

SQUARE ROOT OF A NUMBER

#include
float squareRoot(float n)
{
/*We are using n itself as initial approximation
This can definitely be improved */
float x = n;
float y = 1;
float e = 0.000001; /* e decides the accuracy level*/
while(x - y > e)
{
x = (x + y)/2;
y = n/x;
}
return x;
}

/* Driver program to test above function*/
int main()
{
int n;
scanf("%d",&n);
printf ("Square root of %d is %f", n, squareRoot(n));
getchar();
}

SPOJ :: IS IT TREE

Q.) given an unweighted and undirected graph write a program to check is it a tree or not.
input:
In first line contain n (numbers of nodes) and m (number of edges)
then m lines contain m egdes of grapg (two integer u and v)
1<=N<=10000 ,1<=M<=20000
output:
print YES if it is a tree else print NO.

Just we have to check the graph is connected and have no cycle then it will be tree else no.
----------------------------------------------------------------

#include
#include
#include
#include
using namespace std;

// This class represents a directed graph using adjacency list representation
class Graph
{
    int V;    // No. of vertices
    list *adj;    // Pointer to an array containing adjacency lists
    bool isCyclicUtil(int v, bool visited[], bool *rs);
public:
    Graph(int V);  // Constructor
    void addEdge(int v, int w); // function to add an edge to graph
    bool BFS(int s);  // prints BFS traversal from a given source s
    bool isCyclic();    // returns true if there is a cycle in this graph
};

Graph::Graph(int V)
{
    this->V = V;
    adj = new list[V];
}

void Graph::addEdge(int v, int w)
{
    adj[v].push_back(w); // Add w to v’s list.
}

bool Graph::BFS(int s)
{
    // Mark all the vertices as not visited
    bool *visited = new bool[V];
    for(int i = 0; i < V; i++)
        visited[i] = false;

    // Create a queue for BFS
    list queue;

    // Mark the current node as visited and enqueue it
    visited[s] = true;
    queue.push_back(s);

    // 'i' will be used to get all adjacent vertices of a vertex
    list::iterator i;

    while(!queue.empty())
    {
        // Dequeue a vertex from queue and print it
        s = queue.front();
       // cout << s << " ";
        queue.pop_front();

        // Get all adjacent vertices of the dequeued vertex s
        // If a adjacent has not been visited, then mark it visited
        // and enqueue it
        for(i = adj[s].begin(); i != adj[s].end(); ++i)
        {
            if(!visited[*i])
            {
                visited[*i] = true;
                queue.push_back(*i);
            }
        }
    }
    for(int k=0;k
    {
if(visited[k]==false)
return false;
    }
    return true;
}
bool Graph::isCyclicUtil(int v, bool visit[], bool *recStack)
{
    if(visit[v] == false)
    {
        // Mark the current node as visited and part of recursion stack
        visit[v] = true;
        recStack[v] = true;

        // Recur for all the vertices adjacent to this vertex
        list::iterator i;
        for(i = adj[v].begin(); i != adj[v].end(); ++i)
        {
            if ( !visit[*i] && isCyclicUtil(*i, visit, recStack) )
                return true;
            else if (recStack[*i])
                return true;
        }

    }
    recStack[v] = false;  // remove the vertex from recursion stack
    return false;
}

// Returns true if the graph contains a cycle, else false.

bool Graph::isCyclic()
{
    // Mark all the vertices as not visited and not part of recursion
    // stack
    bool *visit = new bool[V];
    bool *recStack = new bool[V];
    for(int i = 0; i < V; i++)
    {
        visit[i] = false;
        recStack[i] = false;
    }

    // Call the recursive helper function to detect cycle in different
    // DFS trees
    for(int i = 0; i < V; i++)
        if (isCyclicUtil(i, visit, recStack))
            return true;

    return false;
}
int main()
{
int j,n,m,a,b;
scanf("%d %d",&n,&m);
Graph g(n);
for(j=0;j
{
scanf("%d %d",&a,&b);
g.addEdge(a-1,b-1);
}
if(g.BFS(0))
{
if(g.isCyclic())
         cout << "NO"<
     else
         cout << "YES"<
}
else
printf("NO\n");
return 0;
}