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.
Solution
TODO
Code
class MinStack {
Stack<Integer> stack = new Stack();
Stack<Integer> minStack = new Stack();
/** initialize your data structure here. */
public MinStack() {
}
public void push(int x) {
stack.push(x);
int peek = minStack.empty()? x : minStack.peek();
if(x < peek) {
minStack.push(x);
}
else {
minStack.push(peek);
}
}
public void pop() {
stack.pop();
minStack.pop();
}
public int top() {
return stack.peek();
}
public int getMin() {
return minStack.peek();
}
}
Performance
TODO