棧是一種常見的數據結構,主要特點是“後進先出”。以下是用C語言實現的簡單的棧。
頭文件 stack.h ,定義棧的結構體和相關的操作:
#ifndef STACK_H #define STACK_H enum { STACK_OK = 0, STACK_OVERFLOW, STACK_ERROR, }; typedef int ElemType; struct stack { ElemType *data; ElemType *top; int capability; }; void stack_init(struct stack *st, int capability); void stack_destroy(struct stack *st); int stack_push(struct stack *st, ElemType elem); int stack_pop(struct stack *st); ElemType stack_top(const struct stack *st); int stack_size(const struct stack *st); int stack_capability(const struct stack *st); int stack_full(const struct stack *st); int stack_empty(const struct stack *st); void stack_clear(struct stack *st); #endif
C文件 stack.c,實現stack的相關操作。
#include "stack.h" #include <assert.h> #include <stdlib.h> void stack_init(struct stack *st, int capability) { assert(st && capability > 0); st->data = (ElemType *)malloc(sizeof(ElemType) * capability); assert(st->data); st->top = st->data; st->capability = capability; } void stack_destroy(struct stack *st) { assert(st); if (st->data) free(st->data); st->data = 0; st->top = 0; st->capability = 0; } int stack_push(struct stack *st, ElemType elem) { assert(st); if (stack_full(st)) return STACK_OVERFLOW; *(st->top++) = elem; return STACK_OK; } int stack_pop(struct stack *st) { assert(st); if (stack_empty(st)) return STACK_OVERFLOW; st->top--; return STACK_OK; } ElemType stack_top(const struct stack *st) { assert(st); if (stack_empty(st)) return (ElemType)0; else return *(st->top - 1); } int stack_size(const struct stack *st) { assert(st); return (st->top - st->data); } int stack_capability(const struct stack *st) { assert(st); return st->capability; } int stack_full(const struct stack *st) { return (stack_size(st) == stack_capability(st)); } int stack_empty(const struct stack *st) { return (stack_size(st) == 0); } void stack_clear(struct stack *st) { assert(st); st->top = st->data; }
上面在stack.h 中定義了ElemType爲int,是簡單的數據類型。上面的實現也是針對簡單數據庫類型的,對於一些稍複雜的數據類型,上面的實現不適用。例如,如果棧元素需要用某個函數來銷燬,則stack_clear就不適用了。
實現中也用到了assert,不過我不大喜歡用assert,因爲會使程序中止。其實可以用if來作檢測而不中止,或是不作檢測,靠使用者自行判斷。
上面實現也沒有用到 STACK_ERROR 這個值。
下面是提供測試的main.c
#include <stdio.h> #include "stack.h" int main() { struct stack st; int i; stack_init(&st, 5); printf("-------------- init stack ----------------\n"); printf("stack capability: %d\n", stack_capability(&st)); printf("stack size: %d\n", stack_size(&st)); printf("stack empty ? %s\n", stack_empty(&st) ? "Y" : "N"); printf("stack full ? %s\n", stack_full(&st) ? "Y" : "N"); printf("-------------- pushing elements ----------------\n"); for (i = 0; i < 10; ++i) { printf("push %i OK ? %s\n", i, (stack_push(&st, i) == STACK_OK ? "Y" : "N")); printf("stack size: %d\n", stack_size(&st)); printf("stack empty ? %s\n", stack_empty(&st) ? "Y" : "N"); printf("stack full ? %s\n", stack_full(&st) ? "Y" : "N"); } printf("-------------- poping elements ----------------\n"); while (!stack_empty(&st)) { printf("top: %d\n", stack_top(&st)); printf("pop OK? %s\n", stack_pop(&st) == STACK_OK ? "Y" : "N"); printf("stack size: %d\n", stack_size(&st)); printf("stack empty ? %s\n", stack_empty(&st) ? "Y" : "N"); printf("stack full ? %s\n", stack_full(&st) ? "Y" : "N"); } printf("-------------- clear stack ----------------\n"); stack_clear(&st); printf("stack capability: %d\n", stack_capability(&st)); printf("stack size: %d\n", stack_size(&st)); printf("stack empty ? %s\n", stack_empty(&st) ? "Y" : "N"); printf("stack full ? %s\n", stack_full(&st) ? "Y" : "N"); printf("-------------- destroy stack --------------\n"); stack_destroy(&st); return 0; }