Add C example for recursion (#41)

03_recursion/c/01_countdown.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+void countdown(int i) {
+	printf("%d\n", i);
+	
+	// base case
+	if (i <= 0)
+		return;
+	//recursive case
+	else
+		countdown(i - 1);
+}
+
+int main(void) {
+
+	countdown(5);
+	
+	return 0;
+}

03_recursion/c/02_greet.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+void greet2(char *name) {
+	printf("how are you, %s?\n", name);
+}
+
+void bye() {
+	printf("ok bye!\n");
+}
+
+void greet(char *name) {
+	printf("hello, %s!\n", name);
+	greet2(name);
+	printf("getting ready to say bye...\n");
+	bye();
+}
+
+int main(void) {
+	
+	greet("adit");
+
+	return 0;
+}

03_recursion/c/03_factorial.c

@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+int fact(int x) {
+	if (x == 1)
+		return 1;
+	else
+		return x * fact(x - 1);
+}
+
+int main(void) {
+	
+	printf("%d", fact(5));
+
+	return 0;
+}