LeetCode | 20. 有效的括号

typedef int STDataType;
typedef struct Stack
{
  STDataType* a;
  int top;
  int capacity;
}ST;
// 初始化栈
void StackInit(ST* ps)
{
  assert(ps);
  ps->a = NULL;
  ps->capacity = 0;
  //top 表示指向栈顶元素
  //ps->top = -1;
  //top 表示指向栈顶元素的下一个
  ps->top = 0;
}
// 入栈
void StackPush(ST* ps, STDataType x)
{
  assert(ps);
  if (ps->capacity == ps->top)
  {
    STDataType newcapacity = ps->capacity == 0 ? 4 : ps->capacity * 2;
    STDataType* tmp = (STDataType*)realloc(ps->a, sizeof(STDataType) * newcapacity);
    if (tmp == NULL)
    {
      perror("relloc fail!\n");
      exit(-1);
    }
    ps->a = tmp;
    ps->capacity = newcapacity;
  }
  ps->a[ps->top] = x;
  ps->top++;
}
// 出栈
void StackPop(ST* ps)
{
  assert(ps);
  assert(ps->top > 0);
  ps->top--;
}
// 获取栈顶元素
STDataType StackTop(ST* ps)
{
  assert(ps);
  assert(ps->top > 0);
  return ps->a[ps->top - 1];
}
// 获取栈中有效元素个数
int StackSize(ST* ps)
{
  assert(ps);
  return ps->top;
}
// 检测栈是否为空，如果为空返回非零结果，如果不为空返回0
bool StackEmpty(ST* ps)
{
  assert(ps);
  return ps->top == 0;
}
// 销毁栈
void StackDestroy(ST* ps)
{
  assert(ps);
  ps->a = NULL;
  ps->capacity = ps->top = 0;
}
bool isValid(char* s) {
    ST st;
    StackInit(&st);
    while(*s)
    {
        switch(*s)
        {
            case ')':
            case ']':
            case '}':
            {
                if(StackEmpty(&st))
                {
                    StackDestroy(&st);
                    return false;
                }
                char top = StackTop(&st);
                StackPop(&st);
                if((*s == ')' && top != '(')
                || (*s == ']' && top != '[')
                || (*s == '}' && top != '{'))
                {
                    StackDestroy(&st);
                    return false;
                }
                else
                {
                    ++s;
                }
                break;
            }
            case '(':
            case '[':
            case '{':
            {
                StackPush(&st,*s);
                ++s;
                break;
            }
            default:
                break;
        }
    }
    bool ret = StackEmpty(&st);
    StackDestroy(&st);
    return ret;
}