daa-lab/galeShapley.java

import java.util.*;

public class galeShapley {

    static int N;

    static int womanCharToIndex(char ch) {
        return ch - 'W';
    }

    static int manCharToIndex(char ch) {
        return ch - 'A';
    }

    static boolean prefers(int[][] womenPref, int w, int m, int m1) {
        for (int i = 0; i < N; i++) {
            if (womenPref[w][i] == m)
                return true;

            if (womenPref[w][i] == m1)
                return false;
        }
        return false;
    }

    static void galeShapley(int[][] womenPref, int[][] menPref) {

        int[] womenPartner = new int[N];
        boolean[] menFree = new boolean[N];
        int[] nextProposal = new int[N];

        Arrays.fill(womenPartner, -1);
        Arrays.fill(menFree, true);

        int freeCount = N;

        while (freeCount > 0) {

            int m = -1;

            for (int i = 0; i < N; i++) {
                if (menFree[i] && nextProposal[i] < N) {
                    m = i;
                    break;
                }
            }

            if (m == -1)
                break;

            int w = menPref[m][nextProposal[m]];
            nextProposal[m]++;

            if (womenPartner[w] == -1) {
                womenPartner[w] = m;
                menFree[m] = false;
                freeCount--;
            } else {

                int m1 = womenPartner[w];

                if (prefers(womenPref, w, m, m1)) {
                    womenPartner[w] = m;
                    menFree[m] = false;
                    menFree[m1] = true;
                }
            }
        }

        System.out.println("\nStable matching result:");

        for (int i = 0; i < N; i++) {
            System.out.println(
                "Woman " + (char)('W' + i) +
                " is matched with Man " + (char)('A' + womenPartner[i])
            );
        }
    }

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter number of pairs (n): ");
        N = sc.nextInt();

        int[][] menPref = new int[N][N];
        int[][] womenPref = new int[N][N];

        System.out.println("\nEnter Men's Preference Lists:");

        for (int i = 0; i < N; i++) {

            System.out.println("Preferences of Man " + (char)('A' + i) + ":");

            for (int j = 0; j < N; j++) {
                char ch = sc.next().charAt(0);
                menPref[i][j] = womanCharToIndex(ch);
            }
        }

        System.out.println("\nEnter Women's Preference Lists:");

        for (int i = 0; i < N; i++) {

            System.out.println("Preferences of Woman " + (char)('W' + i) + ":");

            for (int j = 0; j < N; j++) {
                char ch = sc.next().charAt(0);
                womenPref[i][j] = manCharToIndex(ch);
            }
        }

        galeShapley(womenPref, menPref);

        sc.close();
    }
}