leetcode——155—— Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
getMin() -- Retrieve the minimum element in the stack.

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class MinStack {
public:
stack<int> stk;
stack<int> min;

void push(int x) {
stk.push(x);
if(min.empty() || x <= min.top())
min.push(x);
}

void pop() {
if(stk.top() == min.top())
{
stk.pop();
min.pop();
}
else
stk.pop();
}

int top() {
return stk.top();
}

int getMin() {
return min.top();
}
};