dynamic_stack.c in C

A growable integer stack backed by malloc and realloc.

#include <stdio.h>
#include <stdlib.h>

typedef struct {
    int *items;
    size_t len;
    size_t cap;
} Stack;

static void push(Stack *s, int value) {
    if (s->len == s->cap) {
        s->cap = s->cap ? s->cap * 2 : 4;
        s->items = realloc(s->items, s->cap * sizeof(int));
    }
    s->items[s->len++] = value;
}

static int pop(Stack *s) {
    return s->len ? s->items[--s->len] : 0;
}

int main(void) {
    Stack s = {0};
    for (int i = 1; i <= 10; i++)
        push(&s, i * i);
    long total = 0;
    while (s.len)
        total += pop(&s);
    printf("sum of squares: %ld\n", total);
    free(s.items);
    return 0;
}

How it works

push doubles capacity with realloc when full.
pop returns and removes the top item.
main fills, drains, and frees the stack.

Keywords and builtins used here

for
if
int
long
main
pop
push
return
size_t
sizeof
static
struct
typedef
void
while

The run, in numbers

Lines: 32
Characters to type: 549
Tokens: 218
Three-star pace: 105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 125 seconds.

Type this snippet

Step 1 of 2 in Encore, step 24 of 25 in Pointers & memory.

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