题解 | #图的闭包#

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);

        while(in.hasNext()){
            solution(in);
        }
    }

    /**
     * 模拟法
     * @param in
     */
    private static void solution(Scanner in){
        // 点数
        int n = in.nextInt();
        // 边数
        int m = in.nextInt();

        boolean[][] hasEdge = new boolean[n+1][n+1];
        int[] degree = new int[n+1];

        int u,v;
        for(int i=1; i<=m; i++){
            u = in.nextInt();
            v = in.nextInt();
            degree[u]++;
            degree[v]++;
            if(u < v){
                hasEdge[u][v] = true;
            }else{
                hasEdge[v][u] = true;
            }
        }

        int result = 0;
        boolean edgeAdded;
        while(true){
            edgeAdded = false;
            for(int i=1; i<=n; i++){
                for(int j=i+1; j<=n; j++){
                    if(degree[i]+degree[j] >= n){
                        if(!hasEdge[i][j]){
                            result++;
                            degree[i]++;
                            degree[j]++;
                            hasEdge[i][j] = true;
                            edgeAdded = true;
                        }
                    }
                }
            }
            // 未加新边 退出
            // 已加新边 重新循环
            if(!edgeAdded){
                break;
            }
        }
        
        System.out.println(result);
    }
}