last pop in stack not working yet

2023-06-30 07:12:43 -07:00
parent 0763ca0cd4
commit cfaf438fd4
3 changed files with 163 additions and 3 deletions
--- a/c/stack.c
+++ b/c/stack.c
@@ -0,0 +1,117 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+/*
+how a stack grows
+
+len = 0  ______
+push: len = 1 [A]
+push: len = 2 [A] <-- [B]             new elements point to the previous top
+push: len = 3 [A] <-- [B] <-- [C]
+pop:  len = 2 [A] <-- [B] <-/- [C] need to free C here and set new head of Stack to be B
+pop:  len = 1 [A] <-/- [B]
+pop:  len = 0 /[A]/
+
+
+ */
+
+typedef struct Node {
+    int          value;
+    struct Node* next;
+} Node;
+
+typedef struct Stack {
+    int   length;
+    Node* head;
+} Stack;
+
+Node* new_node(int value) {
+    Node* n = malloc(sizeof(Node));
+    n->value = value;
+
+    return (n);
+}
+
+Stack* new_stack() {
+    Stack* s = malloc(sizeof(Stack));
+    s->length = 0;
+    s->head = NULL;
+    return (s);
+}
+
+bool pop(Stack* s) {
+    if (s->length == 0) {
+        return false;
+    } else {
+        Node* n = s->head;
+        if (s->length == 1) {
+            s->head = NULL;
+        } else {
+            s->head = n->next;
+        }
+        free(n);
+        s->length--;
+        return true;
+    }
+}
+
+void delete_stack(Stack* s) {
+    while (s->length > 0) {
+        pop(s);
+    }
+}
+
+void push(Stack* s, Node* n) {
+    if (s->length == 0) {
+        s->head = n;
+        s->length++;
+    } else {
+        // make the old head point to what will be the new head
+        n->next = s->head;
+        // make the head point to n now
+        s->head = n;
+        s->length++;
+    }
+}
+
+int main() {
+    Stack* s = new_stack();
+
+    Node* a = new_node(10);
+    Node* b = new_node(11);
+    Node* c = new_node(12);
+    Node* d = new_node(13);
+
+    push(s, a);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+    push(s, b);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+    push(s, c);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+    push(s, d);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+
+    bool res = pop(s);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+
+    res = pop(s);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+
+    res = pop(s);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+
+    res = pop(s);
+    printf("the value at the top of the stack is: %d\n", s->head->value);
+    printf("the length of the stack is: %d\n", s->length);
+
+    // delete_stack(s);
+
+    return (0);
+}