设计桟的min、push以及pop的时间复杂度都是O(1)

题目：定义栈的数据结构，要求添加一个min函数，能够得到栈的最小元素。要求函数min、push以及pop的时间复杂度都是O(1)。

\brief 设计包含min函数的栈定义栈的数据结构，要求添加一个min函数，能够得到栈的最小元素。要求函数min、push以及pop的时间复杂度都是O(1)。这里给出整个栈的简单实现，使用链式栈，利用辅助栈提供min值查询。*/#include <stdio.h>#include <stdlib.h>#include <assert.h> #define SUCCESS 0                   ///< 执行成功#define FAILED -1                   ///< 执行失败 typedef struct _MinStackItem        ///  栈元素{    int data;                       ///< 栈数据    struct _MinStackItem *next;     ///< 下一个栈元素指针} MinStackItem; typedef struct _MinStack            ///  栈{    MinStackItem *top;              ///< 栈链指针    MinStackItem *min;              ///< 栈最小值链指针} MinStack;  /*!创建栈\param pStack 栈指针的地址\return 创建栈成功返回SUCCESS；否则返回FAILED*/int create_stack(MinStack **pStack){    int retVal = FAILED;     if(pStack)    {        MinStack *newStack = malloc(sizeof(MinStack));         if(newStack)        {            newStack->top = NULL;            newStack->min = NULL;             *pStack = newStack;             retVal = SUCCESS;        }    }     return retVal;} /*!测试栈stack是否为空\param stack 栈指针\return 若栈指针为NULL或栈为空返回真；否则返回假*/int stack_isEmpty(const MinStack *stack){    return !stack || (stack && stack->top == NULL);} /*!把整型数据data压入栈stack，时间复杂度O(1)\param stack 栈指针\param data 待压入栈的数据\return 操作成功返回SUCCESS；否则返回FAILED*/int stack_push(MinStack *stack, int data){    int retVal = FAILED;     if(stack)    {        MinStackItem *item = malloc(sizeof(MinStackItem));  //新栈数据节点        MinStackItem *min = malloc(sizeof(MinStackItem));   //新栈最小值节点         if(item && min)        {            item->data = data;            min->data = data;             if(stack->top && stack->min)            {                if(data < stack->top->data)                    min->data = data;                else                    min->data = stack->min->data;            }             /* 插入item节点到stack->top */            item->next = stack->top;            stack->top = item;             /* 插入min节点到stack->min */            min->next = stack->min;            stack->min = min;             retVal = SUCCESS;        }    }     return retVal;} /*!从栈stack中弹出整型数据到data指向的位置，时间复杂度O(1)\param stack 栈指针\param data 弹出元素存放地址\return 操作成功返回SUCCESS；否则返回FAILED*/int stack_pop(MinStack *stack, int *data){    int retVal = FAILED;     if(stack && data)    {        MinStackItem *freePtr = NULL;         /* 断言测试top和min，要么全NULL，要么全不为NULL */        assert((stack->top && stack->min) || (!stack->top && !stack->min));         if(stack->top && stack->min)        {            *data = stack->top->data;       //写入栈顶数据             freePtr = stack->top;           //栈顶指针->freePtr            stack->top = stack->top->next;  //修改栈顶指针，弹出栈顶             free(freePtr);                  //free栈顶指针             freePtr = stack->min;           //栈最小指针->freePtr            stack->min = stack->min->next;  //修改栈最小指针，弹出最小值             free(freePtr);                  //free栈最小指针             retVal = SUCCESS;        }    }     return retVal;} /*!获取当前栈stack的最小值，并存放到min指向的位置，时间复杂度O(1)\param stack 栈指针\param min 当前栈最小值存放地址\return 操作成功返回SUCCESS；否则返回FAILED*/int stack_min(const MinStack *stack, int *min){    int retVal = FAILED;     if(stack && min && stack->min)    {        *min = stack->min->data;         retVal = SUCCESS;    }     return retVal;} /*!销毁栈，并置栈指针为NULL\param pStack 栈指针的地址*/void delete_stack(MinStack **pStack){    if(pStack)    {        MinStack *stack = *pStack;        MinStackItem *freePtr = NULL;         if(stack)        {            /* 释放top链 */            while(stack->top)            {                freePtr = stack->top;                stack->top = stack->top->next;                 free(freePtr);            }             /* 释放min链 */            while(stack->min)            {                freePtr = stack->min;                stack->min = stack->min->next;                 free(freePtr);            }        }         *pStack = NULL;    }} int main(){    int result = FAILED;     int dataSet[] = {10, 4, 2, 3, 1, 5};    //测试数据集    MinStack *stack = NULL;                 //栈     /* 创建栈 */    result = create_stack(&stack);     /* push测试数据 */    {        int i;         for(i = 0; i < sizeof(dataSet) / sizeof(int) && result == SUCCESS; ++ i)        {            result = stack_push(stack, dataSet[i]);            printf("push: %d %s\n", dataSet[i], result == SUCCESS ? "success!" : "failed!");        }    }     /* pop测试数据 */    while(result == SUCCESS && !stack_isEmpty(stack))    {        int data = -1, min = -1;         if(stack_min(stack, &min) == SUCCESS && stack_pop(stack, &data) == SUCCESS)            printf("current min: %d, pop: %d success!\n", min, data);        else            result = FAILED;    }     /* 释放栈 */    delete_stack(&stack);     assert(!stack);     return result;}