3 Cycle

Given a graph with N vertices (numbered from 1 to N) and Two Lists (U,V) of size M where (U[i],V[i]) and (V[i],U[i]) are connected by an edge , then count the distinct 3-cycles in the graph. A 3-cycle PQR is a cycle in which (P,Q), (Q,R) and (R,P) are connected an edge.

Input Format :

Line 1 : Two integers N and M
Line 2 : List u of size of M
Line 3 : List v of size of M

Return Format :

The count the number of 3-cycles in the given Graph

Constraints :

1<=N<=100

1<=M<=(N*(N-1))/2

1<=u[i],v[i]<=N

Sample Input:

3 3
1 2 3
2 3 1

Sample Output:

1

import java.util.Scanner;

public class solution {
    public static int[][] adj = new int[1005][1005];

    public int solve(int n, int m, int U[], int V[]) {
        for (int i = 0; i < m; i++) {
            adj[U[i]][V[i]] = 1;
            adj[V[i]][U[i]] = 1;
        }
        int cycles = 0;
        for (int a = 1; a <= n; a++) {
            for (int b = 1; b <= n; b++)
                if (adj[a][b] == 1) {
                    int u = b;
                    for (int j = 1; j <= n; j++)
                        if (adj[u][j] == 1) {
                            int v = j;
                            if (v == a) // basically working as visisted array
                                continue;
                            if (adj[v][a] == 1) // if a,u,v form a cycle
                                cycles++;
                        }
                }
        }
        return cycles / 6; // A cycle is counted 6 times , (anticlockwise + clockwise )*(from A + from U + from V)
    }
}