Add 155_Min_Stack.java

Author: Sean Prashad

Design/155_Min_Stack.java

@@ -1,27 +1,34 @@
 class MinStack {
- int minimum = Integer.MAX_VALUE;
- Stack<Integer> stack = new Stack<Integer>();
+ private int minVal;
+ private Stack<Integer> s;
+
+ /** initialize your data structure here. */
+ public MinStack() {
+ minVal = Integer.MAX_VALUE;
+ s = new Stack<>();
+ }
 
  public void push(int x) {
- if (x <= minimum) {
- stack.push(minimum);
- minimum = x;
+ if (x <= minVal) {
+ s.push(minVal);
+ minVal = x;
  }
 
- stack.push(x);
+ s.push(x);
  }
 
  public void pop() {
- if (stack.pop() == minimum) {
- minimum = stack.pop();
+ int topOfStack = s.pop();
+ if (minVal == topOfStack) {
+ minVal = s.pop();
  }
  }
 
  public int top() {
- return stack.peek();
+ return s.peek();
  }
 
  public int getMin() {
- return minimum;
+ return minVal;
  }
 }