C++ stack::empty()用法及代碼示例

原型：

    stack<T> st; //declaration
    st.empty();

參數：

    No parameter passed

返回類型：布爾值(真或假)

• 真：堆棧為空
• 錯誤：堆棧不為空

要包含的頭文件：

    #include <iostream>
    #include <stack>
    OR
    #include <bits/stdc++.h>

用法：

該函數檢查堆棧是否為空。

時間複雜度：O(1)

例：

    For a stack of integer,
    stack<int> st;
    st.push(4);
    st.push(5);
    stack content:
    5 <-- TOP
    4
    IF (st.empty())
        Print "Stack is empty"
    Else 
        Print "Stack is not empty"
    
    Output:
    Prints "Stack is not empty"
    st.pop()
    st.pop()
    Stack content:
    Empty stack
    IF (st.empty())
        Print "Stack is empty"
    Else 
        Print "Stack is not empty"
    
    Output:
    Prints "Stack is empty"

C++ 實現：

#include <bits/stdc++.h>
using namespace std;

int main(){
    cout<<"...use of empty function...\n";
    int count=0;
    stack<int> st; //declare the stack
    st.push(4); //pushed 4
    st.push(5); //pushed 5
    st.push(6);
    
    cout<<"stack elements are:\n";
    while(!st.empty()){//stack not empty
        cout<<"top element is:"<<st.top()<<endl;//print top element
        st.pop();
        count++;
    }
    if(st.empty()) //to check for empty stack
    cout<<"stack empty\n";
    cout<<count<<" pop operation performed total to make stack empty\n";
	
    return 0;   
}

輸出

...use of empty function...
stack elements are:
top element is:6
top element is:5
top element is:4
stack empty
3 pop operation performed total to make stack empty