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.
Solution:
class MinStack {
public:
/** initialize your data structure here. */
stack<int> s;
stack<int> m;
MinStack() {
}
void push(int x) {
s.push(x);
if(m.empty() || (m.top() >= x)){
m.push(x);
}
}
void pop() {
if(!s.empty()){
int t = s.top();
s.pop();
if(!m.empty() && m.top() >= t){
m.pop();
}
}
}
int top() {
return s.top();
}
int getMin() {
return m.top();
}
};
/**
* Your MinStack object will be instantiated and called as such:
* MinStack obj = new MinStack();
* obj.push(x);
* obj.pop();
* int param_3 = obj.top();
* int param_4 = obj.getMin();
*/
