Leetcode 155. Min Stack

Author: kalpak92

LeetCode/155. Min Stack/Solution.java

@@ -0,0 +1,67 @@
+//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.
+
+/**
+ * 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();
+ */
+
+class MinStack {
+    
+    class Node
+    {
+        int val;
+        int min;
+        Node next;
+        
+        public Node(int data, int min)
+        {
+            this.val = data;
+            this.min = min;
+        }
+    }
+    Node head;
+
+    /** initialize your data structure here. */
+    public MinStack() {
+        
+    }
+    
+    public void push(int x) {
+        if (head == null)
+            head = new Node(x, x);
+        else{
+            Node newNode = new Node(x, Math.min(x, head.min));
+            newNode.next = head;
+            head = newNode;
+        }
+    }
+    
+    public void pop() {
+        head = head.next;
+    }
+    
+    public int top() {
+        return head.val;
+    }
+    
+    public int getMin() {
+        return head.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();
+ */

Stacks and Queues/SortStack.java

@@ -16,7 +16,7 @@ public static Stack<Integer> sortStack(Stack<Integer> s)
         while(!s.isEmpty())
         {
             int temp = s.pop();
-            while(!result.isEmpty() && result.peek() > temp)
+            while(!result.isEmpty() && result.peek() < temp)
             {
                 s.push(result.pop());
             }