Zigzag (or diagonal) traversal of Matrix in C++

In this problem, we are given a 2D matrix. Our task is to print all the elements of the matric in a diagonal order.

Let’s take an example to understand the problem,

1    2    3
4    5    6
7    8    9

Output −

1
4    2
7    5    3
8    6
9

Let’s see the pattern that is followed while printing the matrix in a zigzag form or diagonal form.

This is the way diagonal traversal works.

The number of lines in output is always dependent on the row and columns of the 2D matrix.

For a 2D matrix mat[r][c], their will be r+c-1 output lines.

Example

Now, let’s see the solution to the program,

 Live Demo

#include <iostream>
using namespace std;
#define R 5
#define C 4
int min2(int a, int b)
{ return (a < b)? a: b; }
int min3(int a, int b, int c)
{ return min2(min2(a, b), c);}
int max(int a, int b)
{ return (a > b)? a: b; }
void printDiagonalMatrix(int matrix[][C]){
   for (int line=1; line<=(R + C -1); line++){
      int start_col = max(0, line-R);
      int count = min3(line, (C-start_col), R);
      for (int j=0; j<count; j++)
      cout<<matrix[min2(R, line)-j-1][start_col+j]<<"\t";
      cout<<endl;
   }
}
int main(){
   int M[R][C] = {{1, 2, 3, 4},
      {5, 6, 7, 8},
      {9, 10, 11, 12},
      {13, 14, 15, 16},
      {17, 18, 19, 20},};
   cout<<"The matrix is : \n";
   for (int i=0; i< R; i++){
      for (int j=0; j<C; j++)
      cout<<M[i][j]<<"\t";
      cout<<endl;
   }
   cout<<"\nZigZag (diagnoal) traversal of matrix is :\n";
   printDiagonalMatrix(M);
   return 0;
}

Output

The matrix is :
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
17 18 19 20
ZigZag (diagonal) traversal of matrix is :
1
5 2
9 6 3
13 10 7 4
17 14 11 8
18 15 12
19 16
20