Question
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.
Example:
MinStack minStack = new MinStack(); minStack.push(-2); minStack.push(0); minStack.push(-3); minStack.getMin(); --> Returns -3. minStack.pop(); minStack.top(); --> Returns 0. minStack.getMin(); --> Returns -2.
Difficulty:Easy
Category:Stack, Design
Analyze
Solution
class MinStack {
public:
/** initialize your data structure here. */
MinStack() {}
void push(int x) {
s_.push(x);
if (s_min.empty() || x <= getMin()) s_min.push(x);
}
void pop() {
if (s_.top() == s_min.top()) s_min.pop();
s_.pop();
}
int top() { return s_.top(); }
int getMin() { return s_min.top(); }
private:
stack<int> s_;
stack<int> s_min;
};