栈（Stack）的C语言实现

栈（Stack）实现的是一个后进先出策略。元素弹出的顺序正好和它们压入的次序相反。S.top表示栈顶元素，S.size表示栈的大小。如果试图对一个S.top=0的栈进行弹出操作，则称栈下溢。如果S.top超过了S.size，则称栈上溢。
这里使用动态分配内存的方式实现栈，并可以动态的调整栈的大小，如有错误敬请指正。

//Item.htypedef struct ITEM {    int key;    void * statellite;} item_t;

//Stack.h#ifndef STDIO_H#define STDIO_H#include <stdio.h>#endif#ifndef STDLIB_H#define STDLIB_H#include <stdlib.h>#endif#ifndef ITEM_H#define ITEM_H#include "Item.h"#endiftypedef struct STACK{    int top;    int size;    item_t* array;} stack_t;int stack_init(stack_t * S, int size);int stack_resize(stack_t * S, int size);int stack_free(stack_t * S);int stack_empty(stack_t * S);int stack_push(stack_t * S, item_t item);int stack_pop(stack_t * S, item_t *item);void stack_info(stack_t * S);

//Stack.c#include "Stack.h"int stack_init(stack_t * S, int size) {    S->top = 0;    S->array = (item_t*)calloc(size, sizeof(item_t));    if (S->array != NULL) {        S->size = size;        return 1;    } else {        S->size = 0;        fprintf(stderr, "Stack init fail.\n");        return 0;    }}int stack_resize(stack_t * S, int size) {    S->array = (item_t*)realloc(S->array, size * sizeof(item_t));    if (S->array != NULL) {        S->size = size;        if (S->top > S->size) {            S->top = S->size;        }        return 1;    } else {        S->top = 0;        S->size = 0;        fprintf(stderr, "Stack resize fail.\n");        return 0;    }}int stack_free(stack_t * S) {    free(S->array);    S->array = NULL;    S->top = 0;    S->size = 0;    return 1;}int stack_empty(stack_t * S) {    if (S->array == NULL) {        fprintf(stderr, "Stack is not initialized.\n");        return 1;    }    if (S->top == 0)        return 1;    else        return 0;}int stack_push(stack_t * S, item_t item) {    if (S->array == NULL) {        fprintf(stderr, "Stack is not initialized.\n");        return 0;    }    if (S->top < S->size) {        S->array[S->top++] = item;        return 1;    } else {        fprintf(stderr, "Stack overflow.\n");        return 0;    }}int stack_pop(stack_t * S, item_t * item) {    if (S->array == NULL) {        fprintf(stderr, "Stack is not initialized.\n");        return 0;    }    if (!stack_empty(S)) {        *item = S->array[--S->top];        return 1;    } else {        fprintf(stderr, "Stack underflow\n");        return 0;    }}void stack_info(stack_t * S) {    static int count = 0;    printf("%d:\n", count++);    if (S->array == NULL) {        printf("stack is not initialized.\n-------------------------------\n");        return;    }    printf("stack top:%d\n", S->top);    printf("stack size:%d\n", S->size);    printf("stack element:\n");    for (int i = S->top - 1; i >= 0; i--) {        printf("%d ", S->array[i].key);    }    printf("\n-------------------------------\n");}