avc278 - 1.01 - Javascript (#53)

Added my two solutions to the Chapter 1 Problem 1 folder.
First solution solves the problem with the use of additional data structures.
Second solution solves the problem without any additional data structures.

Author: avc278

JavaScript/chapter01/p01_is_unique/avc278.js

@@ -0,0 +1,59 @@
+// Is Unique: Implement an algorithm to determine if a string has all unique characters.
+// What if you cannot used additional data structures?
+
+const assert = require("assert");
+
+/**
+ * Checks if a string is composed of all unique characters
+ * @param  {string} str input string to check
+ * @return {bool}       Whether the input string contains unique characters
+ *
+ * We iterate through the input str of length N. Operations within this loop are O(1), so no additional time added.
+ * We create an additional data structure, `set` where in the worst case is the same size as the input str, N.
+ *
+ * Runtime: O(N)
+ * Space:   O(N)
+ *
+ */
+// with additional data structures
+const isUnique1 = (str) => {
+  const strSet = new Set();
+  for (const s of str) {
+    if (strSet.has(s)) return false;
+    strSet.add(s);
+  }
+  return true;
+};
+
+/**
+ * Checks if a string is composed of all unique characters
+ * @param  {string} str input string to check
+ * @return {bool}       Whether the input string contains unique characters
+ *
+ * We iterate through the input str of length N. Within that, we iterate through the rest of the str of length N-1.
+ * Within the nested for loop, we only perform an O(1) operation. This leads to O(N^2) for the runtime complexity.
+ * In this implementation, we do not create any additional data structures, so we use constant space.
+ *
+ * Runtime: O(N^2)
+ * Space:   O(1)
+ */
+// without additional data structures
+const isUnique2 = (str) => {
+  for (let i = 0; i < str.length - 1; i++) {
+    for (let j = i + 1; j < str.length; j++) {
+      if (str[i] === str[j]) return false;
+    }
+  }
+  return true;
+};
+
+describe(module.filename, () => {
+  it("should return true on an input string with unique characters", () => {
+    assert.equal(isUnique1("tech"), true);
+    assert.equal(isUnique2("tech"), true);
+  });
+  it("should return false on an input string with non-unique characters", () => {
+    assert.equal(isUnique1("techqueria"), false);
+    assert.equal(isUnique2("techqueria"), false);
+  });
+});

package.json

@@ -5,5 +5,5 @@
   },
   "scripts": {
     "test": "mocha --recursive 'JavaScript/**/*.js'"
- }
+  }
 }