q073_SetMatrixZeroes.java

package leetcode_algorithm;


import java.util.Arrays;

/**
 * Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.
 * <p>
 * click to show follow up.
 * <p>
 * Follow up:
 * Did you use extra space?
 * 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.
 * Could you devise a constant space solution?
 * <p>
 * Subscribe to see which companies asked this question.
 */

public class q073_SetMatrixZeroes {

    public static void main(String[] args) {
        int[][] nums = new int[][]{
                {0, 1},
                {1, 1}
        };
        new q073_SetMatrixZeroes().setZeroes(nums);
        System.out.println(Arrays.deepToString(nums));
    }

    /**
     * ½â·¨1
     *
     * @param matrix
     */
    public void setZeroes(int[][] matrix) {
        boolean fr = false, fc = false;
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[0].length; j++) {
                if (matrix[i][j] == 0) {
                    if (i == 0) fr = true;
                    if (j == 0) fc = true;
                    matrix[0][j] = 0;
                    matrix[i][0] = 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;
                }
            }
        }

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