Data structure problem 3: Implement a Stack With Minimum

 

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

Implement the MinStack class:

MinStack() initializes the stack object.

void push(int val) pushes the element val onto the stack.

void pop() removes the element on the top of the stack.

int top() gets the top element of the stack.

int getMin() retrieves the minimum element in the stack.

Input

["MinStack","push","push","push","getMin","pop","top","getMin"]

[[],[-2],[0],[-3],[],[],[],[]]

Output

[null,null,null,null,-3,null,0,-2]

Explanation

MinStack minStack = new MinStack();

minStack.push(-2);

minStack.push(0);

minStack.push(-3);

minStack.getMin(); // return -3

minStack.pop();

minStack.top();    // return 0

minStack.getMin(); // return -2

Solution:

 var MinStack = function() {

this.elements = [];
};

/**

 @param {number} x
 @return {void}
 */
MinStack.prototype.push = function(x) {
  this.elements.push({
    value: x,
    min: this.elements.length === 0 ? x : Math.min(x, this.getMin()),
  });
};
/**

 @return {void}
 */
MinStack.prototype.pop = function() {
  this.elements.pop();
};
/**

 @return {number}
 */
MinStack.prototype.top = function() {
  return this.elements[this.elements.length - 1].value;
};
/**

 @return {number}
 */
MinStack.prototype.getMin = function() {
  return this.elements[this.elements.length - 1].min;
};




Explanation: In this approch whenever we are pushing something in stack we are maintaing value and min value element and that does the work .