added armstrong algorithm

src/others/armstrong.js

@@ -0,0 +1,40 @@
+/**
+ * Check if a number is an Armstrong number.
+ *
+ * Returns true if the number is an Armstrong number, false otherwise.
+ *
+ * @public
+ *
+ * @example
+ * var isArmstrong = require('path-to-algorithms/src/others/armstrong').isArmstrong;
+ * var result = isArmstrong(153);
+ *
+ * console.log(result); // true
+ *
+ * @param {Number} num The number to check.
+ * @returns {boolean} True if the number is an Armstrong number, false otherwise.
+ *
+ * @module others/armstrong
+ */
+(function (exports) {
+  'use strict';
+
+  function isArmstrongNumber(num) {
+    if (num < 0) {
+      return false; // Armstrong numbers are non-negative
+    }
+
+    const numStr = num.toString();
+    const numDigits = numStr.length;
+    let sum = 0;
+
+    for (let i = 0; i < numDigits; i++) {
+      const digit = parseInt(numStr[i], 10);
+      sum += Math.pow(digit, numDigits);
+    }
+
+    return sum === num;
+  }
+
+  exports.isArmstrong = isArmstrongNumber;
+})(typeof window === 'undefined' ? module.exports : window);

test/others/armstrong.spec.js

@@ -0,0 +1,34 @@
+var isArmstrong = require('../../src/others/armstrong.js').isArmstrong;
+
+describe('isArmstrong', () => {
+  'use strict';
+  it('should return true for Armstrong numbers', () => {
+    expect(isArmstrong(0)).toBe(true); // 0 is an Armstrong number
+    expect(isArmstrong(1)).toBe(true); // 1 is an Armstrong number
+    expect(isArmstrong(153)).toBe(true); // 153 is an Armstrong number
+    expect(isArmstrong(9474)).toBe(true); // 9474 is an Armstrong number
+  });
+
+  it('should return false for non-Armstrong numbers', () => {
+    expect(isArmstrong(10)).toBe(false); // 10 is not an Armstrong number
+    expect(isArmstrong(123)).toBe(false); // 123 is not an Armstrong number
+    expect(isArmstrong(1234)).toBe(false); // 1234 is not an Armstrong number
+    expect(isArmstrong(9876)).toBe(false); // 9876 is not an Armstrong number
+  });
+
+  it('should return false for negative numbers', () => {
+    expect(isArmstrong(-153)).toBe(false); // Negative numbers are not Armstrong numbers
+    expect(isArmstrong(-9474)).toBe(false); // Negative numbers are not Armstrong numbers
+  });
+
+  it('should return true for single-digit numbers', () => {
+    expect(isArmstrong(0)).toBe(true); // 0 is an Armstrong number
+    expect(isArmstrong(1)).toBe(true); // 1 is an Armstrong number
+    expect(isArmstrong(9)).toBe(true); // 9 is an Armstrong number
+  });
+
+  it('should return true for multi-digit Armstrong numbers', () => {
+    expect(isArmstrong(153)).toBe(true); // 3^3 + 5^3 + 1^3 = 153
+    expect(isArmstrong(9474)).toBe(true); // 9^4 + 4^4 + 7^4 + 4^4 = 9474
+  });
+});