stack stack
last in first out
The top of the stack pointer always points to a mark on the top element of the stack, usually counted as TOP. When there is no element in the stack (that is, the stack is empty), TOP is -1.
Common uses: stack is used to simulate some recursion to prevent the program from limiting the memory of the stack and causing the program to run incorrectly.
1. The definition of stack
Before using it, you need to add the header file first.
#include <stack>
using namespace std;
Access to elements in the stack container:
Due to the first-in, last-out data structure, the stack in STL can only access the top element of the stack through top().
st.top();
2. Common operations of stack
| type | type explanation |
|---|---|
| push | stack |
| top | Pop the top element of the stack |
| pop | pop out |
| empty | Empty |
| size | Get the number of elements in the stack |
Notice:
-
Before using the pop() function and the top() function, you must first use the empty() function to determine whether the stack is empty.
-
STL does not implement the emptying of the stack, and elements can be repeatedly popped out through the while loop until the stack is empty. as follows:
while(!st.empty()){ st.pop(); }
1. push()
Push x onto the stack.
st.push(i);
2. top ()
Directly take the value pointed to by the top element TOP of the stack.
st.top();
3. pop ()
Pop the top element of the stack.
st.pop();
4. empty()
Returns true only if the stack is empty if TOP = -1; otherwise, returns false.
if(st.empty() == true){
}
5. size
Returns the number of elements in the stack.
st.size();