题目-有效的括号
一、分析题目
二、编写代码
typedef char STDataType;
typedef struct Stack
{
STDataType* a; //
int top; //相当于数组下标,注意栈为空时,top的值应该为?
int capacity;//栈的容量
}ST;
void STInit(ST* pst);
void STDestroy(ST* pst);
//入栈
void STPush(ST* pst,STDataType x);
//出栈
void STPop(ST* pst);
//栈顶元素
STDataType STTop(ST* pst);
//判断栈是否为空
bool STEmpty(ST* pst);
//获取size
int STSize(ST* pst);
void STInit(ST* pst)
{
assert(pst);
pst->a = NULL;
pst->top = 0;//top指向-1,表示栈顶元素数据 0 栈顶数据下一位置
pst->capacity = 0;
}
void STDestroy(ST* pst)
{
assert(pst);
free(pst->a);
pst->a = NULL;
pst->top = pst->capacity = 0;
}
//判断栈是否为空
bool STEmpty(ST* pst)
{
assert(pst);
return pst->top == 0;
}
//入栈
void STPush(ST* pst, STDataType x)
{
if (pst->top == pst->capacity)
{
int newCapacity = pst->capacity == 0 ? 4 : pst->capacity * 2;
STDataType* tmp = realloc(pst->a, newCapacity * sizeof(STDataType));
if (tmp == NULL)
{
perror("realloc fail");
return;
}
pst->a = tmp;
pst->capacity = newCapacity;
}
pst->a[pst->top] = x;
pst->top++;
}
//出栈
void STPop(ST* pst)
{
assert(pst);
assert(!STEmpty(pst));
pst->top--;
}
//栈顶元素
STDataType STTop(ST* pst)
{
assert(pst);
assert(!STEmpty(pst));
return pst->a[pst->top - 1];
}
//获取size
int STSize(ST* pst)
{
assert(pst);
return pst->top;
}
bool isValid(char* s) {
ST st;
STInit(&st);
while(*s)
{
if(*s=='['||*s=='{'||*s=='(')
{
STPush(&st,*s);
}
else
{
if(STEmpty(&st)){
STDestroy(&st);
return false;
}
char top = STTop(&st);
STPop(&st);
if((*s == ']'&& top != '[')||(*s=='}'&&top!='{')||(*s==')'&& top !='('))
{
STDestroy(&st);
return false;
}
}
++s;
}
bool ret = STEmpty(&st);
STDestroy(&st);
return ret;
}