Print matrix in zag-zag fashion in C Programming.

In C programming, printing a matrix in zig-zag fashion means traversing the matrix diagonally while alternating the direction of traversal. This creates a zig-zag pattern where elements are visited along diagonals, first from top-left to bottom-right, then from bottom-right to top-left, and so on.

Syntax

void printZigZag(int matrix[][COLS], int rows, int cols);

Example

Here's a complete program that prints a 3x3 matrix in zig-zag fashion −

#include <stdio.h>
#include <stdbool.h>

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

int main() {
    int k = 3, l = 3;
    int mat[][3] = {
        {10, 20, 30},
        {40, 50, 60},
        {70, 80, 90}
    };
    
    int row = 0, col = 0;
    bool flag = false;
    int i, len, diag;
    
    printf("Matrix in zig-zag fashion: ");
    
    int mn = min(k, l);
    
    /* Print first half of diagonals */
    for (len = 1; len <= mn; ++len) {
        for (i = 0; i < len; ++i) {
            printf("%d ", mat[row][col]);
            if (i + 1 == len)
                break;
            if (flag)
                ++row, --col;
            else
                --row, ++col;
        }
        if (len == mn)
            break;
        if (flag)
            ++row, flag = false;
        else
            ++col, flag = true;
    }
    
    /* Move to next starting position */
    if (row == 0) {
        if (col == k - 1)
            ++row;
        else
            ++col;
        flag = true;
    } else {
        if (row == l - 1)
            ++col;
        else
            ++row;
        flag = false;
    }
    
    /* Print second half of diagonals */
    int MAX = max(k, l) - 1;
    for (diag = MAX; diag > 0; --diag) {
        if (diag > mn)
            len = mn;
        else
            len = diag;
            
        for (i = 0; i < len; ++i) {
            printf("%d ", mat[row][col]);
            if (i + 1 == len)
                break;
            if (flag)
                ++row, --col;
            else
                ++col, --row;
        }
        
        if (row == 0 || col == k - 1) {
            if (col == k - 1)
                ++row;
            else
                ++col;
            flag = true;
        } else if (col == 0 || row == l - 1) {
            if (row == l - 1)
                ++col;
            else
                ++row;
            flag = false;
        }
    }
    
    printf("<br>");
    return 0;
}

Matrix in zig-zag fashion: 10 20 40 70 50 30 60 80 90

How It Works

The algorithm works in two phases:

• Phase 1: Traverse diagonals from top-left corner, increasing diagonal length until reaching the middle
• Phase 2: Continue from the appropriate edge position, decreasing diagonal length until reaching bottom-right
• The flag variable controls the direction of traversal within each diagonal
• Direction alternates between each diagonal to create the zig-zag pattern

Conclusion

The zig-zag matrix traversal technique efficiently prints matrix elements diagonally with alternating directions. This approach is useful for various matrix processing problems and demonstrates advanced array indexing techniques in C programming.