C++ stack::top()用法及代碼示例

原型：

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

參數：

    No parameter passed

返回類型：T //數據類型

要包含的頭文件：

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

用法：

該函數返回堆棧的當前頂部元素。 (堆棧狀態沒有變化)

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

    int temp=st.top() //5
    Print temp // prints 5
    stack content://same as before, it don't change stack status
    5 <-- TOP
    4

C++ 實現：

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

int main(){
    cout<<"...use of top 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++;
    }
    cout<<"stack empty\n";
    cout<<count<<" pop operation performed total to make stack empty\n";
    return 0;   
}

輸出

...use of top 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