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2013
11-09

POJ 1466 Girls and Boys [解题报告] Java

Girls and Boys

问题描述 :

In the second year of the university somebody started a study on the romantic relations between the students. The relation “romantically involved” is defined between one girl and one boy. For the study reasons it is necessary to find out the maximum set satisfying the condition: there are no two students in the set who have been “romantically involved”. The result of the program is the number of students in such a set.

输入:

The input contains several data sets in text format. Each data set represents one set of subjects of the study, with the following description:

the number of students

the description of each student, in the following format

student_identifier:(number_of_romantic_relations) student_identifier1 student_identifier2 student_identifier3 …

or

student_identifier:(0)

The student_identifier is an integer number between 0 and n-1 (n <=500 ), for n subjects.

输出:

For each given data set, the program should write to standard output a line containing the result.

样例输入:

7
0: (3) 4 5 6
1: (2) 4 6
2: (0)
3: (0)
4: (2) 0 1
5: (1) 0
6: (2) 0 1
3
0: (2) 1 2
1: (1) 0
2: (1) 0

样例输出:

5
2

解题代码:

//* @author: Yeming Hu"[email protected]"
import java.util.*;

/**
 *
 * @author yeming
 */
public class Main {

    static int n;
    static LinkedList< Integer>[] matrix;
    static int[] result;
    static boolean[] state;
    static int ans;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        while(sc.hasNextInt()) {
            init(sc);
            for(int i = 0; i < n; i++) {
                Arrays.fill(state, false);
                if (find(i)) {
                    ans++;
                }
            }
            System.out.println(n-ans/2);
        }
    }

    private static boolean find(int i) {
        for(int t : matrix[i]) {
            if(!state[t]) {
                state[t] = true;
                if(result[t] == -1
                        || find(result[t])) {
                    result[t] = i;
                    return true;
                }
            }
        }
        return false;
    }

    private static void init(Scanner sc) {
        ans = 0;
        n = sc.nextInt();
        matrix = (LinkedList< Integer>[])new LinkedList[n];
        for(int i = 0; i < n; i++) {
            sc.next();//id, the same as i
            String str = sc.next();
            String numStr = str.substring(1, str.length()-1);
            int num = Integer.parseInt(numStr);
            matrix[i] = new LinkedList< Integer>();
            for (int j = 0; j < num; j++) {
                int id = sc.nextInt();
                matrix[i].add(id);
            }
        }
        state = new boolean[n];
        Arrays.fill(state, false);
        result = new int[n];
        Arrays.fill(result, -1);
    }
}