20. 有效的括号

https://leetcode.cn/problems/valid-parentheses/solutions/2771702/20-you-xiao-de-gua-hao-by-joker-ek4-zsmo

C可能的写法，不用STL

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#include <stdio.h>
#include <stdlib.h>

#define MaxSize 10000
// #define SIZE(a) (sizeof(a) / sizeof(a[0]))
typedef char ElemType;
typedef struct
{
    ElemType data[MaxSize];
    int top;
} SqStack;
void InitStack(SqStack &S);
bool StackEmpty(SqStack S);
bool Push(SqStack &S, ElemType x);
bool Pop(SqStack &S, ElemType &x);
bool GetTop(SqStack S, ElemType &x);
bool bracketCheck(char str[], int length);
// int SIZE(char a[]);
int main()
{
    char str[] = "[]";
    int ret = bracketCheck(str, 2);
    printf("%d", ret);
    return 0;
}
// int SIZE(char a[])
// {
//     return sizeof(a) / sizeof(a[0]);
// }
void InitStack(SqStack &S)
{
    S.top = -1;
}
bool StackEmpty(SqStack S)
{
    return S.top == -1;
}
bool Push(SqStack &S, ElemType x)
{
    if (S.top == MaxSize - 1)
        return false;
    S.data[++S.top] = x;
    return true;
}
bool Pop(SqStack &S, ElemType &x)
{
    if (StackEmpty(S))
        return false;
    x = S.data[S.top--];
    return true;
}
bool GetTop(SqStack S, ElemType &x)
{
    if (StackEmpty(S))
        return false;
    x = S.data[S.top];
    return true;
}
bool bracketCheck(char str[], int length)
{
    SqStack S;
    InitStack(S);
    for (int i = 0; i < length; i++)
    {
        if (str[i] == '(' || str[i] == '[' || str[i] == '{')
            Push(S, str[i]);
        else
        {
            if (StackEmpty(S))
                return false;
            char topElem;
            Pop(S, topElem);
            if (str[i] == ')' && topElem != '(')
                return false;
            if (str[i] == ']' && topElem != '[')
                return false;
            if (str[i] == '}' && topElem != '{')
                return false;
        }
    }
    return StackEmpty(S);
}

1047. 删除字符串中的所有相邻重复项

https://leetcode.cn/problems/remove-all-adjacent-duplicates-in-string/solutions/2777120/1047-shan-chu-zi-fu-chuan-zhong-de-suo-y-3yk7

150. 逆波兰表达式求值

https://leetcode.cn/problems/evaluate-reverse-polish-notation/solutions/2777448/150-ni-bo-lan-biao-da-shi-qiu-zhi-by-jok-bew5