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/**

* 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.

*

*/

import java.util.SortedMap;

import java.util.TreeMap;

class MinStack {

SortedMap<Integer, Integer> map = new TreeMap<>();;

Stack<Integer> st = new Stack<>();

/** initialize your data structure here. */

public MinStack() { }

public void push(int x) {

if (map.containsKey(x)) {

map.put(x, map.get(x)+1);

} else {

map.put(x, 1);

}

st.push(x);

}

public void pop() {

Integer topEle = st.peek();

int count = map.get(topEle);

count--;

if (count <= 0) {

map.remove(topEle);

} else {

map.put(topEle, count);

}

st.pop();

}

public int top() {

return st.peek();

}

public int getMin() {

return map.firstKey();

}

}

/**

* https://discuss.leetcode.com/topic/4953/share-my-java-solution-with-only-one-stack

*/

class MinStack2 {

static class Element

{

final int value;

final int min;

Element(final int value, final int min)

{

this.value = value;

this.min = min;

}

}

final Stack<Element> stack = new Stack<>();

public void push(int x) {

final int min = (stack.empty()) ? x : Math.min(stack.peek().min, x);

stack.push(new Element(x, min));

}

public void pop()

{

stack.pop();

}

public int top()

{

return stack.peek().value;

}

public int getMin()

{

return stack.peek().min;

}

}

/**

* https://discuss.leetcode.com/topic/4953/share-my-java-solution-with-only-one-stack

*/

class MinStack3 {

long min;

Stack<Long> stack;

public MinStack(){

stack=new Stack<>();

}

public void push(int x) {

if (stack.isEmpty()){

stack.push(0L);

min=x;

}else{

stack.push(x-min);//Could be negative if min value needs to change

if (x<min) min=x;

}

}

public void pop() {

if (stack.isEmpty()) return;

long pop=stack.pop();

if (pop<0) min=min-pop;//If negative, increase the min value

}

public int top() {

long top=stack.peek();

if (top>0){

return (int)(top+min);

}else{

return (int)(min);

}

}

public int getMin() {

return (int)min;

}

}

/**

* 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();

*/