Print matrix in zag-zag fashion in C Programming.

Given a matrix mat[row][col] we have to print the given matrix in zig-zag fashion like in the given image below −

So the output should be like −

Output: 10 20 40 70 50 30 60 80 90

For the above problem, we have followed a simple approach where we have to iterate the matrix diagonally and change the value of iteration to change the direction after every previous match.

Algorithm

START
STEP 1-> DECALRE AND SET k = 3, l = 3
STEP 2-> DECLARE A MATRIX mat[][3]
STEP 3-> DECLARE AND SET row = 0, col = 0, flag = false;
STEP 4-> SET mn = MINIMUM(k, l)
STEP 5-> LOOP FOR len = 1 AND len <= mn AND ++len
   LOOP FOR i = 0 AND i < len AND ++i
      PRINT mat[row][col]
      IF i + 1 == len THEN,
         BREAK
      END IF
      IF flag THEN,
         INCREMENT row BY 1 AND DECREMENT col BY 1
      ELSE
         DECREMENT row BY 1 AND INCREMENT col BY 1
      END IF
   END FOR
   IF len == mn THEN,
      BREAK
   END IF
   IF flag THEN
      INCREMENT row BY 1 AND SET flag = FALSE
   ELSE
      INCREMENT col BY 1 AND SET flag = TRUE
   END IF
END FOR
STEP 6-> IF row == 0 THEN,
   IF col == k – 1 THEN,
      INCREMENT row BY 1
   ELSE
      INCREMENT col BY 1
   END IF
   SET flag = 1
   ELSE
      IF row == l – 1 THEN,
         INCREMENT col BY 1
      ELSE
         INCREMENT row BY 1
   SET flag = 0
END IF
STEP 7-> SET MAX = MAXIMUM(k, l) – 1
STEP 8-> LOOP FOR len, diag = MAX AND diag > 0 AND --diag
   IF diag > mn THEN,
      SET len = mn
   ELSE
   SET len = diag
   END IF
   FOR i = 0 AND i < len AND ++i
      PRINT mat[row][col]
   IF i + 1 == len THEN,
      BREAK
   END IF
   IF flag THEN,
      INCREMENT row BY 1 AND DECREMENT col BY 1
   ELSE
      INCREMENT col BY 1 AND DECREMENT row BY 1
   END IF
   IF row == 0 || col == k – 1 THEN,
      IF col == k - 1
         INCREMENT row BY 1
      ELSE
         INCREMENT col BY 1
      END IF
      SET flag = true
      ELSE IF col == 0 || row == l – 1 THEN,
         IF row == l – 1 THEN,
            INCREMENT col BY 1
         ELSE
            INCREMENT row BY 1
         END IF
         SET flag = false
      ENF IF
   END FOR
STOP

Example

 Live Demo

#include <stdio.h>
#include <stdbool.h>
#define C 3
#define min(a, b) a>b?b:a
#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, j, len, diag;
   int MAX;
   int mn = min(k, l); //to check the minimum number and return that minimum number
   for ( len = 1; len <= mn; ++len) {
      for ( i = 0; i < len; ++i) {
         printf("%d ", mat[row][col]); //Printing the matrix in zigzag format
         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;
   }
   if (row == 0) {
      if (col == k - 1)
         ++row;
      else
         ++col;
         flag = 1;
   } else {
      if (row == l - 1)
         ++col;
      else
         ++row;
      flag = 0;
   }
   MAX = max(k, l) - 1; //To check the maximum element
   for ( len, diag = MAX; diag > 0; --diag) { //Loop to go diagonally.
      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;
      }
   }
   return 0;
}

Output

This Program will Print output −

10 20 40 70 50 30 60 80 90