Hamed Kiani (Ph.D.)
  • Home
  • Publications
  • Contact

If an element in an M * N matrix is 0, set its entire row and column to 0 (c++)

7/20/2015

0 Comments

 
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
/******************************************************************************************
*******************************************************************************************
Chapter 1 Arrays and Strings

 * Write an algorithm such that if an element in an M * N matrix is 0,
 * its entire row and column is set to 0;
 
By: Hamed Kiani (July 20, 2015)
******************************************************************************************
******************************************************************************************/

#include<iostream>
#include<cstring>

using namespace std;

const int row = 3, col = 3;

void print_mat(double **mat, int row, int col)
{
        for (int i = 0; i < row; i++) {
                for (int j = 0; j < col; j++)
                        cout << " " << mat[i][j];
                cout << endl;
        }
}

// space O(n), time O(n^2)
void zero_in_matrix(double **mat)
{
        
        // int zero_row = (int) malloc(sizeof(int) * row)
        int zero_row[row] = {0};
        //int *zero_row = (int*) malloc(sizeof(int) * row);
        
        // int zero_col = (int) malloc(sizeof(int) * col)
        int zero_col[col] = {0};
        //int *zero_col = (int*) malloc(sizeof(int) * col);

        // keep the indices of zero values in mat
        for (int i = 0 ; i < row; i++)
                for (int j = 0 ; j < col; j++)
                {
                        if (mat[i][j] == 0){
                                zero_row[i] = 1;
                                zero_col[j] = 1;
                        }
                }
        
        // che if there is a zero, change all values of the colum and row to zero
        for (int i = 0 ; i < row; i++)
                for (int j = 0 ; j < col; j++)
                {
                        if ((zero_row[i] == 1) | (zero_col[j] == 1))
                                mat[i][j] = 0;
                }
}

void main() {

        double **mat;
        //int col, row;

        cout << " # or rows: " << row << endl;
        // cin >> row;

        cout << " # or cols: " << col << endl;
        // cin >> col;


        mat = (double **) malloc(sizeof(double *) * row);
        
        for (int i = 0; i < row; i++)
                mat[i] = (double *) malloc(sizeof(double) * col);

        for (int i = 0; i < row; i++)
                for (int j = 0; j < col; j++)
                        cin >> mat[i][j];

        cout << " the original matrix: " << endl;
        print_mat(mat, row, col);

        zero_in_matrix(mat);

        cout << " the matrix after zeroing: " << endl;
        print_mat(mat, row, col);       
}
0 Comments



Leave a Reply.

    A place to practice the coding interview.

    Author

    Hamed Kiani

    Categories

    All
    Arrays And Strings
    Linked List
    Stack And Queue
    Trees And Graphs

    Archives

    September 2015
    July 2015

    RSS Feed

Copyright © 2020, Hamed Kiani