added lec04

section01/Lec04/change.c

+#include <stdio.h>
+#include <stdlib.h>
+
+struct change{
+    int quarters;
+    int dimes;
+    int nickels;
+    int pennies;
+};
+
+struct change *make_change(float amount)
+{
+    int cents = amount * 100;
+    struct change *c = malloc(sizeof(*c));
+    c->quarters = 0;
+    c->dimes = 0;
+    c->nickels = 0;
+    c->pennies = 0;
+
+    while (cents > 0){
+        if (cents > 25){
+            c->quarters ++;
+            cents -= 25;
+        } else if (cents > 10){
+            c->dimes ++;
+            cents -= 10;
+        } else if (cents > 5){
+            c->nickels ++;
+            cents -= 5;
+        } else{
+            c->pennies = cents;
+            cents = 0;
+        }
+    }
+
+    return c;
+}
+
+void print_change(struct change* c)
+{
+    printf("%d quarters, %d dimes, %d nickels, %d pennies\n",
+                c->quarters, c->dimes, c->nickels, c->pennies);
+}
+
+int main(void){
+    struct change *c;
+    float amount;
+
+    printf("amount: $");
+    scanf("%f", &amount);
+
+    c = make_change(amount);
+    print_change(c);
+
+    free(c);
+    c = NULL; // don't leave dangling pointer
+}