edit 155

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_155.java

@@ -2,59 +2,67 @@
 
 import java.util.*;
 
-/**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:
- _155 minStack = new _155();
- minStack.push(-2);
- minStack.push(0);
- minStack.push(-3);
- minStack.getMin();   --> Returns -3.
- minStack.pop();
- minStack.top();      --> Returns 0.
- minStack.getMin();   --> Returns -2.
+/**
+ * 155. Min Stack
+ * 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.
  */
+
 public class _155 {
-    
-    private Stack<Integer> stack;
-    private int min;
-
-    /** initialize your data structure here. */
-    public _155() {
-        stack = new Stack();
-        min = Integer.MAX_VALUE;
-    }
-    
-    public void push(int x) {
-        /**All the trick happens here, we push the second minimum number onto the stack before we push the newer one,
-         * this way, when popping, we could always get the next minimum one in constant time.*/
-        if(x <= min){
-            stack.push(min);
-            min = x;
+
+    public static class MinStack {
+        private Stack<Integer> stack;
+        private int min;
+
+        /**
+         * initialize your data structure here.
+         */
+        public MinStack() {
+            stack = new Stack();
+            min = Integer.MAX_VALUE;
         }
-        stack.push(x);
-    }
-    
-    public void pop() {
-        if(min == stack.peek()){
-            stack.pop();
-            min = stack.pop();
-        } else {
-            stack.pop();
+
+        public void push(int x) {
+            /**All the trick happens here, we push the second minimum number onto the stack before we push the newer one,
+             * this way, when popping, we could always get the next minimum one in constant time.*/
+            if (x <= min) {
+                stack.push(min);
+                min = x;
+            }
+            stack.push(x);
+        }
+
+        public void pop() {
+            if (min == stack.peek()) {
+                stack.pop();
+                min = stack.pop();
+            } else {
+                stack.pop();
+            }
+            if (stack.isEmpty()) min = Integer.MAX_VALUE;
+        }
+
+        public int top() {
+            return stack.peek();
+        }
+
+        public int getMin() {
+            return min;
         }
-        if(stack.isEmpty()) min = Integer.MAX_VALUE;
-    }
-    
-    public int top() {
-        return stack.peek();
-    }
-    
-    public int getMin() {
-        return min;
     }
 
 }