Implement constantTimeStackMin.js

constantTimeStackMin/constantTimeStackMin.js

@@ -6,23 +6,43 @@
 /**
   * Stack Class
   */
-  var Stack = function() {
+var Stack = function () {
+  var storage  = {};
+  var minSoFar = [];
+  var top      = 0;
 
   // add an item to the top of the stack
-  this.push = function(value){
+  this.push = function (value) {
+    if ( minSoFar.length === 0 || value <= minSoFar[minSoFar.length - 1] ) {
+      minSoFar.push( value );
+    }
+    storage[top] = value;
+    top += 1;
   };
 
   // remove an item from the top of the stack
-  this.pop = function(){
+  this.pop = function () {
+    var popped;
+    if ( this.size() > 0) {
+      popped = storage[top - 1];
+      delete storage[top - 1];
+      top -= 1;
+
+      if ( popped === minSoFar[minSoFar.length - 1] ) {
+        minSoFar.pop();
+      }
+      return popped;
+    }
   };
 
   // return the number of items in the stack
-  this.size = function(){
-  }
+  this.size = function () {
+    return top;
+  };
 
-  this.min = function() {
+  this.min = function () {
+    return minSoFar[minSoFar.length - 1];
+  };
 
-  }
   return this;
-};
-
+};