leetcode-solutions/src/leetcode/SetMatrixZeroes.java at master · eko1995/leetcode-solutions · GitHub

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package leetcode;

/**
 * @author eko
 * @date 2018/10/23 7:49 PM
 *
 * Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place.
 *
 * Example 1:
 *
 * Input:
 * [
 *   [1,1,1],
 *   [1,0,1],
 *   [1,1,1]
 * ]
 * Output:
 * [
 *   [1,0,1],
 *   [0,0,0],
 *   [1,0,1]
 * ]
 * Example 2:
 *
 * Input:
 * [
 *   [0,1,2,0],
 *   [3,4,5,2],
 *   [1,3,1,5]
 * ]
 * Output:
 * [
 *   [0,0,0,0],
 *   [0,4,5,0],
 *   [0,3,1,0]
 * ]
 * Follow up:
 *
 * A straight forward solution using O(mn) space is probably a bad idea.
 * A simple improvement uses O(m + n) space, but still not the best solution.
 */
public class SetMatrixZeroes {
    public static void main(String[] args) {
        int[][] matrix =
                {
                        {1, 1, 1},
                        {1, 0, 1},
                        {1, 1, 1}
                };

        new SetMatrixZeroes().setZeroes(matrix);

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

    public void setZeroes(int[][] matrix) {
        if (matrix.length == 0) return;
        boolean firstRow = false;
        boolean firstCol = false;

        for (int i = 0; i < matrix[0].length; i++) {
            if (matrix[0][i] == 0) {
                firstRow = true;
                break;
            }
        }

        for (int i = 0; i < matrix.length; i++) {
            if (matrix[i][0] == 0) {
                firstCol = true;
                break;
            }
        }

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

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

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

        if (firstRow) {
            for (int i = 0; i < matrix[0].length; i++) {
                matrix[0][i] = 0;
            }
        }

        if (firstCol) {
            for (int i = 0; i < matrix.length; i++) {
                matrix[i][0] = 0;
            }
        }
    }
}