实现一个简单的字符栈

stack.h

#define STACK_CAPACITY 1000
class Stack {
private:
    char* array;
    int pos;
public:
    Stack(); // constructor for a stack
    void push( char c ); // adds c to the top of the stack
    char pop(); // removes top element, returns it
    char top(); // returns the top element, w/o removing
    bool isEmpty(); // returns true iff the stack is empty
    bool isFull(); // returns true iff the stack is full
    ~Stack(); // destructor for a stack
};

Stack::Stack() {
    pos=0;
    array = new char[STACK_CAPACITY];
}

void Stack::push(char c) {
    if(!isFull()){
        array[pos++] = c;//将c插入到pos位置，pos自增1
    }
}

char Stack::pop() {
    if(!isEmpty()){
        return array[--pos];//top自减1，返回top位置的值
    }
}

char Stack::top() {
    if(!isEmpty())
        return array[pos-1];//top指向下一个值的位置，故应该减1;
}

bool Stack::isEmpty() {
    return !(bool)pos;
}

bool Stack::isFull() {
    return pos>=STACK_CAPACITY;
}

Stack::~Stack() {
    pos=0;
    delete array;
    array = NULL;
}