#2665: Counter II; solution & tests

Author: vetalapo

javascript/src/2665-counterII.js

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+/**
+ * 2665
+ * Counter II
+ **
+ * Write a function createCounter.
+ * It should accept an initial integer init.
+ * It should return an object with three functions.
+ *
+ * The three functions are:
+ *   • increment() increases the current value by 1 and then returns it.
+ *   • decrement() reduces the current value by 1 and then returns it.
+ *   • reset() sets the current value to init and then returns it.
+ *
+ * Example 1:
+ *   Input: init = 5, calls = ["increment","reset","decrement"]
+ *   Output: [6,5,4]
+ *   Explanation:
+ *     const counter = createCounter(5);
+ *     counter.increment(); // 6
+ *     counter.reset(); // 5
+ *     counter.decrement(); // 4
+ *
+ * Example 2:
+ *   Input: init = 0, calls = ["increment","increment","decrement","reset","reset"]
+ *   Output: [1,2,1,0,0]
+ *   Explanation:
+ *     const counter = createCounter(0);
+ *     counter.increment(); // 1
+ *     counter.increment(); // 2
+ *     counter.decrement(); // 1
+ *     counter.reset(); // 0
+ *     counter.reset(); // 0
+ *
+ * Constraints:
+ *   • -1000 <= init <= 1000
+ *   • 0 <= calls.length <= 1000
+ *   • calls[i] is one of "increment", "decrement" and "reset"
+ *
+ * Hint 1:
+ *   You can return an object with methods.
+ *
+ * Hint 2:
+ *   Initialize a variable for currentCount.
+ *   Inside these methods,
+ *   add the appropriate logic which mutates currentCount.
+ **
+ * https://leetcode.com/problems/counter-ii/
+***/
+
+/**
+ * @param {integer} init
+ * @return { increment: Function, decrement: Function, reset: Function }
+***/
+const createCounter = function(init) {
+    let count = init;
+
+    return {
+        increment() {
+            return ++count;
+        },
+        decrement() {
+            return --count;
+        },
+        reset() {
+            return (count = init);
+        }
+    }
+};
+
+/**
+ * const counter = createCounter(5)
+ * counter.increment(); // 6
+ * counter.reset(); // 5
+ * counter.decrement(); // 4
+***/
+
+module.exports = createCounter;

javascript/src/tests/2665-counterII.test.js

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+const createCounter = require("../2665-counterII");
+
+test("Returns a function", () => {
+    const counter = createCounter(0);
+
+    expect(typeof(counter)).toBe("object");
+    expect(typeof(counter.increment)).toBe("function");
+    expect(typeof(counter.decrement)).toBe("function");
+    expect(typeof(counter.reset)).toBe("function");
+});
+
+test("Positive input", () => {
+    const init = 5;
+    const counter = createCounter(init);
+    
+    expect(counter.increment()).toBe(6);
+    expect(counter.reset()).toBe(init);
+    expect(counter.decrement()).toBe(4);
+});
+
+test("Zero input", () => {
+    const init = 0;
+    const counter = createCounter(init);
+    
+    expect(counter.increment()).toBe(1);
+    expect(counter.increment()).toBe(2);
+    expect(counter.decrement()).toBe(1);
+    expect(counter.reset()).toBe(init);
+    expect(counter.reset()).toBe(init);
+});