73. Set Matrix Zeroes

/*
 * 73. Set Matrix Zeroes 
 QuestionEditorial Solution  My Submissions
Total Accepted: 70785
Total Submissions: 208447
Difficulty: Medium
Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.

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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?

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 */
package matrix;

import java.util.*;

public class SetZeroes {
 public void setZeroes(int[][] matrix) {
  // https://discuss.leetcode.com/topic/15193/my-ac-java-o-1-solution-easy-to-read
  int m = matrix.length;
  int n = matrix[0].length;
  boolean fc = false, fr = false;

  for (int i = 0; i < m; i++) {
   for (int j = 0; j < n; 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 < m; i++) {
   for (int j = 1; j < n; j++) {
    if (matrix[i][0] == 0 || matrix[0][j] == 0) {
     matrix[i][j] = 0;
    }
   }
  }

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

 }

 public static void main(String[] args) {
  int[][] matrix = { { 1, 2, 0, 9, 5 }, { 1, 0, 7, 9, 5 }, { 6, 4, 7, 8, 5 }, { 3, 2, 7, 9, 5 },
    { 4, 1, 7, 9, 0 } };
  for (int i = 0; i < matrix.length; i++)
   System.out.println(Arrays.toString(matrix[i]));

  SetZeroes sz = new SetZeroes();
  sz.setZeroes(matrix);
  System.out.println("after set zeroes");
  for (int i = 0; i < matrix.length; i++)
   System.out.println(Arrays.toString(matrix[i]));
  /*
   * after set zeroes [0, 0, 0, 0, 0] [0, 0, 0, 0, 0] [6, 0, 0, 8, 0] [3,
   * 0, 0, 9, 0] [0, 0, 0, 0, 0]
   * 
   */
 }

}