Đảo ngược chuỗi bằng sử dụng stack

// Compiler gcc with Code::Block

#include <stdio.h>

struct node {
    char ch;
    struct node *next;
};

typedef struct node* NODEPTR;

void Init(NODEPTR *plist) {
    *plist = NULL;
}

int Empty(NODEPTR plist) {
    if (plist == NULL )
        return 1;
    return 0;
}

void Push(NODEPTR *plist, char chr) {
    NODEPTR p = (NODEPTR) malloc(sizeof(struct node));
    p->ch = chr;
    p->next = NULL;
    if (Empty(*plist))
        *plist = p;
    else {
        p->next = *plist;
        *plist = p;
    }
}

void Pop(NODEPTR *plist, char *chr) {
    if (!Empty(*plist)) {
        NODEPTR p = *plist;
        *plist = (*plist)->next;
        *chr = p->ch;
        free(p);
    }
}

int main() {
    NODEPTR p;
    Init(&p);
    char st[100];
    printf(" - Enter string: ");
    gets(st);
    int i, n = strlen(st);

    for (i = 0; i < n; i++)
        Push(&p, st[i]);
    for (i = 0; i < n; i++)
        Pop(&p, &st[i]);

    st[n] = '\0';

    printf(" - New string: %s", st);
    return 0;
}