add

1 files changed, 90 insertions, 0 deletions

diff --git a/data_structures/chapter_3/stack_array.c b/data_structures/chapter_3/stack_array.c
new file mode 100644
index 0000000..4c23334
--- /dev/null
+++ b/data_structures/chapter_3/stack_array.c
@@ -0,0 +1,90 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "stack_array.h"
+
+#define EMPTY_TOS (-1);
+#define MIN_STACK_SIZE (5);
+
+struct stack_record
+{
+    int capacity;
+    int top_of_stack;
+    elem *array;
+}
+
+stack create_stack(int max_elements)
+{
+    stack s;
+
+    if(max_elements < MIN_STACK_SIZE)
+        printf("size too small.\n");
+
+    s = malloc(sizeof(struct stack_record));
+    if(s == NULL)
+        printf("out of space");
+
+    s->array = malloc(sizeof(elem) * max_elements);
+
+    if(s->array == NULL)
+        printf("out of space");
+
+    s->capacity = max_elements;
+    make_empty(s);
+
+    return s;
+}
+
+void dispose_stack(stack s)
+{
+    if(s != NULL) {
+        free(s->array);
+        free(s);
+    }
+}
+
+int is_empty(stack s)
+{
+    return s->top_of_stack == EMPTY_TOS;
+}
+
+void make_empty(stack s)
+{
+    s->top_of_stack = EMPTY_TOS;
+}
+
+void push(elem x, stack s)
+{
+    if(s->top_of_stack >= capacity)
+        printf("full stack");
+    else 
+        s->array[++s->top_of_stack] = x;
+    
+}
+
+elem top(stack s)
+{
+    if(!is_empty(s))
+        return s->array[s->top_of_stack];
+
+    printf("empty stack");
+    return 0;
+}
+
+void pop(stack s)
+{
+    if(!is_empty(s))
+        s->top_of_stack--;
+
+    printf("empty stack");
+}
+
+elem top_and_pop(stack s)
+{
+    if(!is_empty(s))
+        /* take care of this, before return, s->top_of_stack is already dec. */
+        return s->array[s->top_of_stack--];
+
+    printf("empty stack");
+    return 0;
+}