docs: sync pattern examples with .c files and fix code blocks

Author: Varunraj-53

21_pattern_examples.md

@@ -3,7 +3,7 @@
 <div align="right">
 
 **🧭 Navigation** 
-[⬅️ Previous](20_typedef.md) | [🏠 Home](README.md) | [➡️ Next](21_pattern_examples.md)
+[⬅️ Previous](20_typedef.md) | [🏠 Home](README.md) | [➡️ Next](README.md)
 
 </div>
 
@@ -256,7 +256,10 @@ int main() {
 
 ---
 
+**Code:** 
+Runnable source: [contributions/basic_programs/pattern_hollow_square.c](../contributions/basic_programs/pattern_hollow_square.c)
 
+```c
 /*
  * Hollow Square Pattern
  *
@@ -265,9 +268,7 @@ int main() {
  * - Only the border (first row, last row, first column, last column)
  * is printed with '*'.
  * - The inner cells are printed with spaces to make the square hollow.
- *
- 
- 
+
  */
 
 #include <stdio.h>
@@ -277,97 +278,91 @@ int main() {
 
  for (int i = 1; i <= n; i++) {
   for (int j = 1; j <= n; j++) {
-
-  // Print star on the boundary, space inside
-  if (i == 1 || i == n || j == 1 || j == n) {
+  if (i == 1 || i == n || j == 1 || j == n)
  printf("* ");
-  } else {
+ else
  printf(" ");
-  }
+
   }
  printf("\n");
  }
  return 0;
 }
+```
+
 **Expected output:**
 ```
-  * * * *
- * *
- * *
- * *
-  * * * *
+* * * * *
+*  *
+*  *
+*  *
+* * * * *
 ```
 ---
 
+ **Code:** 
+Runnable source: [contributions/basic_programs/pattern_diamond.c](../contributions/basic_programs/pattern_diamond.c)
+
+```c
 /*
  * Diamond Star Pattern
  *
  * Explanation:
- * - The diamond is created using two pyramids:
- *  1. Upper pyramid (increasing stars)
- *  2. Lower inverted pyramid (decreasing stars)
- * - For each line:
- *  - First print spaces to center the stars.
- *  - Then print (2*i - 1) stars to maintain symmetric shape.
- 
+ * - The diamond is created using:
+ * 1. Upper pyramid
+ * 2. Lower inverted pyramid
+ * - Each row is centered using spaces.
  */
 
 #include <stdio.h>
 
 int main() {
  int n = 5;
 
- // Upper half of diamond
+ // Upper half
  for (int i = 1; i <= n; i++) {
-  // Print leading spaces
-  for (int s = 1; s <= n - i; s++) {
-  printf(" ");
-  }
-  // Print stars
-  for (int j = 1; j <= 2*i - 1; j++) {
-  printf("*");
-  }
+  for (int s = 1; s <= n - i; s++) printf(" ");
+  for (int j = 1; j <= 2*i - 1; j++) printf("*");
  printf("\n");
  }
 
- // Lower half of diamond
+ // Lower half
  for (int i = n - 1; i >= 1; i--) {
-  for (int s = 1; s <= n - i; s++) {
-  printf(" ");
-  }
-  for (int j = 1; j <= 2*i - 1; j++) {
-  printf("*");
-  }
+  for (int s = 1; s <= n - i; s++) printf(" ");
+  for (int j = 1; j <= 2*i - 1; j++) printf("*");
  printf("\n");
  }
 
  return 0;
 }
+```
+
 **Expected output:**
 ```
- 
- *
- ***
- *****
- *******
- *********
- *******
- *****
- ***
- *
+ *
+ ***
+ *****
+ *******
+*********
+ *******
+ *****
+ ***
+ *
 ```
+
 ---
 
+ **Code:** 
+Runnable source: [contributions/basic_programs/pattern_hollow_pyramid.c](../contributions/basic_programs/pattern_hollow_pyramid.c)
+
+```c
 /*
  * Hollow Pyramid Pattern
  *
  * Explanation:
- * - A pyramid with its inside hollow.
- * - For each row:
- *  * Print leading spaces to center the pyramid.
- *  * Print 1 star at the start and 1 star at the end.
- *  * For the last row, print all stars to close the shape.
- 
+ * - Spaces center the pyramid.
+ * - First and last positions print stars.
+ * - Last row prints all stars.
  */
 
 #include <stdio.h>
@@ -377,35 +372,31 @@ int main() {
 
  for (int i = 1; i <= n; i++) {
 
-  // Print leading spaces
-  for (int s = 1; s <= n - i; s++) {
-  printf(" ");
-  }
+  // Leading spaces
+  for (int s = 1; s <= n - i; s++) printf(" ");
 
-  // Print hollow pattern
   for (int j = 1; j <= 2*i - 1; j++) {
-
-  // First star, last star, or entire last row
-  if (j == 1 || j == 2*i - 1 || i == n) {
+  if (j == 1 || j == 2*i - 1 || i == n)
  printf("*");
-  } else {
+ else
  printf(" ");
-  }
+
   }
 
  printf("\n");
  }
 
  return 0;
 }
-**Expected output:**
 ```
 
- *
- * *
- * *
- * *
- *********
+**Expected output:**
+```
+ *
+ * *
+ * *
+ * *
+*********
 ```
 ---
 
@@ -422,6 +413,7 @@ int main() {
 <div align="right">
 
 **🧭 Navigation** 
-[⬅️ Previous](20_typedef.md) | [🏠 Home](README.md) | [➡️ Next](21_pattern_examples.md)
+[⬅️ Previous](20_typedef.md) | [🏠 Home](README.md)
+
 
 </div>