Acdream 1213 matrix multiplication (matrix multiplication)

Matrix MultiplicationTime limit:2000/1000ms (java/others) Memory limit:128000/64000kb (java/others) Submit statistic Next problem problem DescriptionLet us consider undirected graph G = {V; E} which has N vertices and M edges. Incidence matrix of this graph was nxm matrix A = {A I,j}, such that A i,j are 1 if i-th Vertex is one of the ends of j-t H Edge and 0 in the other case. Your task is to find the sum of all elements of the matrix A TA. InputThe first line of the input file contains the integer numbers-n and M (2≤n≤10 000, 1≤m≤100 000). Then 2*m integer numbers follow, forming M pairs, each pair describes one edge of the graph. All edges is different and there are no loops (i.e. edge ends is distinct). OutputOutput the only number-the sum requested. Sample Input

4 4
1 2
1 3
2 3
2 4

Sample Output

18

Actually is a matrix, oneself by oneself, drawing can understand the second

Java:

Import java.util.*;
Import java.io.*;
Import java.math.*;

public class main{
	static final int MAXN = 10000 + 5;
	static int [] MP = new INT[MAXN];
	public static void Main (String [] agrv)
	throws IOException
	{
		//system.setin (new FileInputStream (" D: "+ file.separator +" Imput.txt "));
		Scanner cin = new Scanner (system.in);
		int N, M, u, v;
		while (Cin.hasnext ()) {
			N = Cin.nextint ();
			M = Cin.nextint ();
			Arrays.fill (MP, 1, N + 1, 0);
			for (int i = 1;i <= M; i + +) {
				u = cin.nextint ();
				v = cin.nextint ();
				if (U = = v) mp[v] + +;
				else {
					Mp[v] + +;
					Mp[u] + +;
				}
			}
			Long ans = 0;
			for (int i = 1;i <= n;i + +) {
				ans + = (long) mp[i] * mp[i];
			}
			System.out.println (ANS);}}