brand new story

/*    implewment (almost) ALL the methods in this class.
 *
 *
 *    This project is based on Chapter 3, section 5, Matrices of Relations
 *
 *    Good luck
 */

import java.util.*;
import java.lang.Math;
/**
 *
 * @author
 * @version (a version number or a date)
 */
public class FunctionsChapter3StylePart2
{
    int[][] matrix;

    public FunctionsChapter3StylePart2(int[][] r)
    {
        matrix = r;
    }

    public int getNumRows()
    {
        return matrix.length;
    }

    public int getNumCols()
    {
        return matrix[0].length;
    }

    /*
     *    replaces the current relation instance variable with r
     *
     *    YES - this method gets used in the my (stipulator) tester
     */
    public void setRelation(int[][] r)
    {
        matrix = r;
    }

    /*
     *    returns the current relation instance variable
     */
    public int[][] getRelation()
    {
        return matrix;
    }

    /*
     *    retruns the number of Order Pairs in the relation
     *      that is, the number of one's (1) in the Matrix
     */
    public int getSize()
    {
        int count = 0;
        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[0].length; j++){
                if(matrix[i][j] == 1){
                    count++;
                }
            }
        }
        return count;
    }

    /*
     *    f is a function if
     *       for each x in X, there is exactly one y in Y with (x,y) in f
     *    returns true if the matrix forms a function
     *    returns false otherwise
     */
    public boolean isFunction()
    {
        for(int i = 0; i < matrix.length; i++){
            int count = 0;
            for(int j = 0; j < matrix[0].length; j++){
                count += matrix[i][j];
            }
            if(count != 1) return false;
        }
        return true;
    }

    /*
     *    A function f from X to Y is said to be one to one if
     *    for each y in Y, there is at most one x in X with f(x) = y
     *
     *    returns true if the matrix is a function and the function is one to one
     *    returns false otherwise
     */
    public boolean isOneToOne()   // column sum is one for every column
    {
        for(int j = 0; j < matrix[0].length; j++){
            int count = 0;
            for(int i = 0; i < matrix.length; i++){
                count += matrix[i][j];
            }
            if(count != 1) return false;
        }
        return true;
    }

    /*
     *    A function from X to Y is said to be onto if
     *    the range of f == Y
     *
     *    returns true if the matrix is a function and the function is onto
     *    returns false otherwise
     */
    public boolean isOnTo()    // column sum > 0 for all columns
    {
        for(int j = 0; j < matrix[0].length; j++){
            int count = 0;
            for(int i = 0; i < matrix.length; i++){
                count += matrix[i][j];
            }
            if(count == 0) return false;
        }
        return true;
    }

    /*
     *     returns true if the matrix is a function and the function is bijective
     *              that is both one to one and onto
     *     returns false otherwise
     */
    public boolean isBijective()
    {
        return isFunction() && isOnTo() && isOneToOne();
    }

    /*
     *   precondition:  comp is a function.
     *
     *   returns a new FunctionsChapter3StylePart2 Object.
     *   The domain of the new Object is this.domain
     *   The coDomain of the new Object is comp.coDomain
     *
     *   The new function is the composition: relation o b = b ( relation )
     *
     *   See the tester for more information
     */
    public FunctionsChapter3StylePart2 composition(int[][] comp)
    {
        int[][] a = new int[matrix.length][comp[0].length];

        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[0].length; j++){
                if(matrix[i][j] > 0){
                    for(int k = 0; k < comp[0].length; k++){
                        if(comp[j][k] > 0){
                            a[i][k] = 1;
                        }
                    }
                }
            }
        }

        FunctionsChapter3StylePart2 two = new FunctionsChapter3StylePart2(a);
        return two;
    }

    /*
     *   precondition:  relation is a function.
     *   rel does not have to be both 1-1 and onto
     *   the inverse does not need to be a function
     */
    public int[][] getInverse()
    {
        int[][] temp = new int[matrix.length][matrix[0].length];
        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[0].length; j++){
                temp[i][j] = matrix[j][i];
            }
        }
        return temp;
    }

    /*
     * A relation is reflexive if (x, x) in R for every x in X
     *
     *       returns true if the current relation is reflexive
     *       returns false otherwise
     *
     *       You shuld not assume the matrix is a square matrix.
     */
    public boolean isReflexive()
    {
        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[0].length; j++){
                if(i == j && i < matrix[0].length && j < matrix.length){
                    if(matrix[i][j] == 0)
                        return false;
                }
            }
        }
        return true;
    }

    /*
     *       A relation is symmetric if
     *       for all x, y in X, if (x,y) in R, then (y,x) in R
     *
     *       returns true if the current relation is symmetric
     *       returns false otherwise
     */
    public boolean isSymmetric()
    {
        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[0].length; j++){
                if(!((matrix[i][j] > 0 && matrix[j][i] > 0)|| (matrix[i][j] == 0 && matrix[j][i] == 0)))
                    return false;
            }
        }
        return true;
    }

    /*
     *       A relation is Antisymmetric if
     *       for all x, y in X, if (x,y) in R, and (y,x) in R, then x = y
     *
     *    returns true if the current relation is Antisymmetric
     *    returns false otherwise
     */
    public boolean isAntiSymmetric()
    {
        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[0].length; j++){
                if(i != j && (matrix[i][j] > 0 && matrix[j][i] > 0))
                    return false;
            }
        }
        return true;
    }

    /*
     *       A relation is transitive:
     *       if (a,b) and (b,c) then (a,c)
     *
     *       returns true if the current relation is transitive
     *       returns false otherwise
     */
    public boolean isTransitive()
    {
        int[][] a = Matrix.product(matrix,matrix);

        for(int i = 0; i < matrix.length; i++){
            for(int j = 0; j < matrix[0].length; j++){
                if(a[i][j] > 0 && matrix[i][j] == 0)
                    return false;
            }
        }
        return true;
    }

    /*
     *    returns true is the relation is an Equivalence Relation
     *    returns false otherwise
     */
    public boolean isEquivalenceRelation()
    {
        return isReflexive() && isTransitive() && isSymmetric();
    }

    /*
     *    returns true is the relation is an Partially Order
     *    returns false otherwise
     */
    public boolean isPartiallyOrder()
    {
        return isReflexive() && isTransitive() && isAntiSymmetric();
    }

    /*
     *     look at the tester
     *
     *    returns [[a, c, ....d], [...], ...[]]
     */
    public String toString()
    {
        String str = "[";
        for(int i = 0; i < matrix.length-1; i++){
            str += "[";
            for(int j = 0; j < matrix[0].length-1; j++){
                str += Integer.toString(matrix[i][j]) + ", ";
            }
            str += Integer.toString(matrix[i][matrix[0].length-1]) + "], ";
        }
        str += "[";
        for(int j = 0; j < matrix[0].length-1; j++){
            str += Integer.toString(matrix[matrix.length-1][j]) + ", ";
        }
        str += Integer.toString(matrix[matrix.length-1][matrix[0].length-1]) + "]]";

        return str;
    }
}