Stacks are a type of container adaptors with LIFO(Last In First Out) type of working, where a new element is added at one end and (top) an element is removed from that end only.
top() function is used to reference the top(or the newest) element of the stack.
Syntax :
stackname.front() Parameters : No value is needed to pass as the parameter. Returns : Direct reference to the top element of the stack container.
Examples:
Input : stackname.push(5);
stackname.push(1);
stackname.top();
Output : 1
Input : stackname.push(5);
stackname.push(1);
stackname.push(2);
stackname.top();
Output : 2
Errors and Exceptions
1. If the stack container is empty, it causes undefined behaviour
2. It has a no exception throw guarantee if the stack is not empty
// CPP program to illustrate // Implementation of top() function #include <iostream> #include <stack> using namespace std; int main() { stack<int> mystack; mystack.push(5); mystack.push(1); mystack.push(2); // Stack top cout << mystack.top(); return 0; } |
Output:
2
Application :
Given a stack of integers, find the sum of the all the integers.
Input : 1, 8, 3, 6, 2 Output: 20
Algorithm
1. Check if the stack is empty, if not add the top element to a variable initialised as 0, and pop the top element.
2. Repeat this step until the stack is empty.
3. Print the final value of the variable.
// CPP program to illustrate // Application of top() function #include <iostream> #include <stack> using namespace std; int main() { int sum = 0; stack<int> mystack; mystack.push(1); mystack.push(8); mystack.push(3); mystack.push(6); mystack.push(2); // Stack becomes 1, 8, 3, 6, 2 while (!mystack.empty()) { sum = sum + mystack.top(); mystack.pop(); } cout << sum; return 0; } |
Output:
20
This article is attributed to GeeksforGeeks.org
leave a comment
0 Comments