added stack live code

slides/exemples/stack.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#define MAX_CAPACITY 5
+
+struct stack {
+    int top;
+    int data[MAX_CAPACITY];
+};
+
+void stack_init(struct stack *s) {
+    s->top = -1;
+}
+
+bool stack_is_empty(struct stack s) {
+    return s.top == -1;
+}
+
+void stack_push(struct stack *s, int val) {
+    if (s->top != MAX_CAPACITY - 1) {
+        s->top += 1;
+        s->data[s->top] = val;
+    }
+}
+
+/*int stack_pop(struct stack *s) {*/
+/*    if (!stack_is_empty(*s)) {*/
+/*        int tmp = s->data[s->top];*/
+/*        s->top -= 1;*/
+/*        return tmp;*/
+/*    }*/
+/*}*/
+
+/*void stack_pop(struct stack *s, int *val) {*/
+/*    if (!stack_is_empty(*s)) {*/
+/*        *val = s->data[s->top];*/
+/*        s->top -= 1;*/
+/*    }*/
+/*}*/
+
+int *stack_pop(struct stack *s) {
+    if (!stack_is_empty(*s)) {
+        int *val = &(s->data[s->top]);
+        s->top -= 1;
+        return val;
+    } else {
+        return NULL;
+    }
+}
+
+int *stack_peek(struct stack s) {
+    if (!stack_is_empty(s)) {
+        int *val = &(s.data[s.top]);
+        return val;
+    } else {
+        return NULL;
+    }
+}
+
+void stack_print(struct stack s) {
+    for (int i = s.top; i >= 0; --i) {
+        printf("%d\n", s.data[i]);
+    }
+}
+
+int main() {
+    struct stack s;
+    stack_init(&s);
+    stack_print(s);
+
+    printf("s.top = %d\n", s.top);
+    printf("is_empty(): %s\n", stack_is_empty(s) ? "True" : "False");
+    stack_push(&s, 10);
+    stack_push(&s, 20);
+    stack_push(&s, 30);
+    stack_push(&s, 40);
+    stack_push(&s, 50);
+    stack_push(&s, 60);
+    printf("is_empty(): %s\n", stack_is_empty(s) ? "True" : "False");
+    stack_print(s);
+    /*int val = -1;*/
+    /*stack_pop(&s, &val);*/
+    /*printf("popped value = %d\n", val);*/
+    /*stack_pop(&s, &val);*/
+    /*printf("popped value = %d\n", val);*/
+    /*stack_pop(&s, &val);*/
+    /*printf("popped value = %d\n", val);*/
+    /*stack_pop(&s, &val);*/
+    /*printf("popped value = %d\n", val);*/
+    /*stack_pop(&s, &val);*/
+    /*printf("popped value = %d\n", val);*/
+    /*stack_pop(&s, &val);*/
+    /*printf("popped value = %d\n", val);*/
+
+    /*printf("popped value = %d\n", stack_pop(&s));*/
+    /*printf("popped value = %d\n", stack_pop(&s));*/
+    /*printf("popped value = %d\n", stack_pop(&s));*/
+    /*printf("popped value = %d\n", stack_pop(&s));*/
+    /*printf("popped value = %d\n", stack_pop(&s));*/
+    /*printf("popped value = %d\n", stack_pop(&s));*/
+
+    printf("peeked value = %d\n", *stack_peek(s));
+    printf("peeked value = %d\n", *stack_peek(s));
+    stack_print(s);
+
+    printf("popped value = %d\n", *stack_pop(&s));
+    printf("popped value = %d\n", *stack_pop(&s));
+    printf("popped value = %d\n", *stack_pop(&s));
+    printf("popped value = %d\n", *stack_pop(&s));
+    printf("popped value = %d\n", *stack_pop(&s));
+    /*printf("popped value = %d\n", *stack_pop(&s));*/
+    stack_print(s);
+    printf("is_empty(): %s\n", stack_is_empty(s) ? "True" : "False");
+
+    return EXIT_SUCCESS;
+}