链表实现栈

题目来源：LeetCode739

// 链表节点
typedef struct Node {
    int value;    // 气温
    int index;    // 下标
    struct Node *next;
} pNode;

// 栈
typedef struct MyStack {
    pNode *top;
} pMyStack;

/**
* @brief 创建栈
* @return 指向栈的指针
*/
pMyStack* CreateStack()
{
    pMyStack *temp = (pMyStack*)malloc(sizeof(pMyStack));
    if (temp == NULL) {
        printf("Failed to request memory");
        exit(1);
    }

    temp->top = NULL;
    return temp;
}

/**
* @brief 判断栈是否为空
* @param 指向栈的指针
* @return 1 栈为空，0 栈不为空
*/
int IsEmpty(pMyStack *obj)
{
    return obj->top == NULL;
}


/**
* @brief 入栈
* @param obj 指向栈的指针
* @param value 气温
* @param index 下标
*/
void Push(pMyStack *obj, int value, int index)
{
    pNode *temp = (pNode*)malloc(sizeof(pNode));
    if (temp == NULL) {
        printf("Failed to request memory");
        exit(1);
    }

    temp->value = value;
    temp->index = index;
    temp->next = obj->top;
    obj->top = temp;
}

/**
* @brief 出栈
* @param obj 指向栈的指针
*/
void Pop(pMyStack *obj)
{
    if (obj->top != NULL) {
        pNode *temp = obj->top;
        obj->top = obj->top->next;
        free(temp);
    }
}

/**
* @brief 获取栈顶的气温
* @param obj 指向栈的指针
* @return 栈顶的气温
*/
int GetTopValue(pMyStack *obj)
{
    if (obj->top != NULL) {
        return obj->top->value;
    } else {
        exit(1);
    }
}

/**
* @brief 获取栈顶的下标
* @param obj 指向栈的指针
* @return 栈顶的下标
*/
int GetTopIndex(pMyStack *obj)
{
    if (obj->top != NULL) {
        return obj->top->index;
    } else {
        return -1;
    }
}

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* dailyTemperatures(int* T, int TSize, int* returnSize)
{
    *returnSize = TSize;
    int *result = (int*)malloc(sizeof(int) * TSize);
    pMyStack *myStack = CreateStack();

    for (int i = TSize - 1; i >= 0; i--) {
        if (i == TSize - 1) {
            result[i] = 0;
            Push(myStack, T[i], i);
            continue;
        }

        //找出后边第一个比今天气温高的日子
        while (!IsEmpty(myStack)) {
            if (GetTopValue(myStack) <= T[i]) {
                Pop(myStack);
            } else {
                result[i] = GetTopIndex(myStack) - i;
                break;
            }
        }

        //栈为空说明后边没有比今天气温高的日子
        if (IsEmpty(myStack)) {
            result[i] = 0;
        }

        Push(myStack, T[i], i);
    }

    return result;
}