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Celebrity Problem
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Celebrity Problem
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// Java program to find celebrity
import java.util.*;
class GFG {
// Max # of persons in the party
static final int N = 8;
// Person with 2 is celebrity
static int MATRIX[][] = { { 0, 0, 1, 0 },
{ 0, 0, 1, 0 },
{ 0, 0, 0, 0 },
{ 0, 0, 1, 0 } };
static int knows(int a, int b) { return MATRIX[a][b]; }
// Returns -1 if celebrity
// is not present. If present,
// returns id (value from 0 to n-1).
static int findCelebrity(int n)
{
// the graph needs not be constructed
// as the edges can be found by
// using knows function
// degree array;
int[] indegree = new int[n];
int[] outdegree = new int[n];
// query for all edges
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
int x = knows(i, j);
// set the degrees
outdegree[i] += x;
indegree[j] += x;
}
}
// find a person with indegree n-1
// and out degree 0
for (int i = 0; i < n; i++)
if (indegree[i] == n - 1 && outdegree[i] == 0)
return i;
return -1;
}
// Driver code
public static void main(String[] args)
{
int n = 4;
int id = findCelebrity(n);
if (id == -1)
System.out.print("No celebrity");
else
System.out.print("Celebrity ID " + id);
}
}
// This code is contributed by Rajput-Ji
// Java program to find celebrity
import java.util.*;
class GFG {
// Max # of persons in the party
static final int N = 8;
// Person with 2 is celebrity
static int MATRIX[][] = { { 0, 0, 1, 0 },
{ 0, 0, 1, 0 },
{ 0, 0, 0, 0 },
{ 0, 0, 1, 0 } };
static int knows(int a, int b) { return MATRIX[a][b]; }
// Returns -1 if celebrity
// is not present. If present,
// returns id (value from 0 to n-1).
static int findCelebrity(int n)
{
// the graph needs not be constructed
// as the edges can be found by
// using knows function
// degree array;
int[] indegree = new int[n];
int[] outdegree = new int[n];
// query for all edges
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
int x = knows(i, j);
// set the degrees
outdegree[i] += x;
indegree[j] += x;
}
}
// find a person with indegree n-1
// and out degree 0
for (int i = 0; i < n; i++)
if (indegree[i] == n - 1 && outdegree[i] == 0)
return i;
return -1;
}
// Driver code
public static void main(String[] args)
{
int n = 4;
int id = findCelebrity(n);
if (id == -1)
System.out.print("No celebrity");
else
System.out.print("Celebrity ID " + id);
}
}