Add Day 8: Intro to pointers

Author: sahilbansal17

Day 8/README.md

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+## Programs for Day 8
+1. [Nested Loop: Pattern printing](nestedLoopPattern.c)
+2. [Two functions to swap numbers](swap.c)
+
+    The first function doesn't work. We try to understand why that doesn't work.
+    An introduction to pointers and memory is provided. 
+    Referencing and Dereferencing operators are discussed.

Day 8/nestedLoopPattern.c

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+/*
+ * A program to print the pattern:
+ 		*
+ 		* * 
+ 		* * *
+ 		....
+ */
+
+#include <stdio.h>
+
+int main () {
+
+	int n;
+	scanf("%d", &n);
+
+	/* Using nested loops:
+	 *  // outer loop: number of rows
+	 *	for (int i = 1; i <= n; i ++) {
+	 *		// inner loop: print i character
+	 *		for (int j = 1; j <= i; j ++) {
+	 *			printf("* ");
+	 *		}
+	 *		// after i-th row is printed entirely, we need to print '\n'
+	 *		printf("\n");
+	 * 	}
+	*/
+
+	// Using just one loop
+
+	int lineNo = 1;
+	int count = 0;
+	while (lineNo <= n) {
+		if (count < lineNo) {
+			printf("* ");
+			count ++;
+		} else {
+			printf("\n");
+			count = 0;
+			lineNo ++;
+		}
+	}
+
+	return 0;
+}

Day 8/swap.c

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+/*
+ * A program to swap two numbers
+ */
+
+#include <stdio.h>
+
+// Incorrect
+void swap1 (int x, int y) {
+	int temp;
+	// to save the original value of x
+	temp = x;
+	// to get value of y in x
+	x = y;
+	// to get original x's value in y
+	y = temp;
+}
+
+// Correct
+void swap2(int *x, int *y) {
+	int temp = *x; // c = a
+	*x = *y; // a = b
+	*y = temp; // b = c
+}
+
+int main () {
+
+	int x, y;
+	scanf("%d %d", &x, &y);
+
+	// call function => function's name and the arguments to it
+	// swap1(x, y);
+
+	swap2(&x, &y);
+	printf("x = %d, y = %d", x, y);
+
+	return 0;
+}