Merge pull request knaxus#36 from knaxus/problems

Implementation of 2 stacks using 1 array

Author: ashokdey

README.md

@@ -14,16 +14,19 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
 ### Data Structures
 
 - [Singly Linked List](src/_DataStructures_/LinkedList)
+
   - [N Element From Last](src/_DataStructures_/LinkedList/element-from-last)
   - [Middle Node](src/_DataStructures_/LinkedList/middle-node)
   - [Detect Loop](src/_DataStructures_/LinkedList/loop-in-list)
   - [Reverse Linked List](src/_DataStructures_/LinkedList/reverse-linked-list)
+
 - [Stack](src/_DataStructures_/Stack)
 
   - [Implement Queue Using Stack](src/_DataStructures_/Stack/immitate-queue-using-stack)
   - [Baseball Game](src/_DataStructures_/Stack/baseball-game)
   - [Minimum Stack](src/_DataStructures_/Stack/min-stack)
   - [Balanced Parenthesis](src/_DataStructures_/Stack/balanced-parenthesis)
+  - [Implement 2 Stacks using Single Array](src/_DataStructures_/Stack/2-stacks-using1-array)
 
 - [Queue](src/_DataStructures_/Queue)
   - [Weave](src/_DataStructures_/Queue/weave)

src/_DataStructures_/Stack/2-stacks-using1-array/index.js

@@ -0,0 +1,85 @@
+/**
+ * Revision to PR #35 where I implemented bullshit thinking of
+ * new breakthrough :D
+ */
+
+class TwoStacks {
+  constructor(capacity) {
+    this.data = [];
+    this.top1 = -1;
+    this.top2 = capacity;
+    this.overflow = new Error('Overflow: Stack is full');
+
+    this.capacity = capacity;
+  }
+
+  push1(value) {
+    if (this.top1 < this.top2 - 1) {
+      this.top1 += 1;
+      this.data[this.top1] = value;
+    } else {
+      throw this.overflow;
+    }
+  }
+
+  push2(value) {
+    if (this.top1 < this.top2 - 1) {
+      this.top2 -= 1;
+      this.data[this.top2] = value;
+    } else {
+      throw this.overflow;
+    }
+  }
+
+  pop1() {
+    if (this.top1 >= 0) {
+      const item = this.data[this.top1];
+      delete this.data[this.top1];
+      this.top1 -= 1;
+      return item;
+    }
+    return -1;
+  }
+
+  pop2() {
+    if (this.top2 < this.capacity) {
+      const item = this.data[this.top2];
+      delete this.data[this.top2];
+      this.top2 += 1;
+      return item;
+    }
+    return -1;
+  }
+}
+
+module.exports = TwoStacks;
+
+/** Test cases */
+
+/*
+const s = new TwoStacks(4);
+
+s.push1('a');
+console.log(s.data);
+
+s.push2('a2');
+console.log(s.data);
+
+s.push1('b');
+console.log(s.data);
+
+s.push2('b2');
+console.log(s.data);
+
+s.push2('d2');
+console.log(s.data);
+
+s.push2('c23');
+console.log(s.data);
+
+console.log(s.pop2());
+console.log(s.data);
+
+console.log(s.pop1());
+console.log(s.data);
+*/