CareerCup 150

C.C 1.7

/**
 * 1.7 Write an algorithm such that if an element in an MxN matrix is 0, its
 * entire row and column are set to 0.
 *
 * @author Jiateng
 */
public class CC1_7 {

    public static void setZeroes(int[][] matrix) {
        boolean firstrow = false;
        boolean firstcolumn = false;

        //check first row
        for (int i = 0; i < matrix[0].length; i++) {
            if (matrix[0][i] == 0) {
                firstrow = true;
                break;
            }
        }
        //check first column
        for (int i = 0; i < matrix.length; i++) {
            if (matrix[i][0] == 0) {
                firstcolumn = true;
                break;
            }
        }
        //if inside matrix has 0; set the related position in firstrow and firstcolumn 0
        for (int i = 1; i < matrix.length; i++) {
            for (int j = 1; j < matrix[0].length; j++) {
                if (matrix[i][j] == 0) {
                    matrix[i][0] = 0;
                    matrix[0][j] = 0;
                }
            }
        }
        //if firstrow or firstcolumn is 0, set that column or row all 0
        for (int i = 1; i < matrix.length; i++) {
            for (int j = 1; j < matrix[0].length; j++) {
                if (matrix[i][0] == 0 || matrix[0][j] == 0) {
                    matrix[i][j] = 0;
                }
            }
        }
        //set the firstcolumn
        if (firstcolumn) {
            for (int i = 0; i < matrix.length; i++) {
                matrix[i][0] = 0;
            }
        }
        //set the firstrow
        if (firstrow) {
            for (int i = 0; i < matrix[0].length; i++) {
                matrix[0][i] = 0;
            }
        }
    }

    public static void main(String[] args) {
        int[][] matrix = new int[][]{{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 0, 1, 2}};
        setZeroes(matrix);

        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[0].length; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println(" ");
        }
    }
}