feat: added Polynomial in Maths (#397)

Maths/Polynomial.js

@@ -0,0 +1,82 @@
+
+/**
+ * Polynomials are algebraic expressions consisting of two or more algebraic terms.
+ * Terms of a polynomial are:
+ * 1. Coefficients e.g. 5, 4 in 5x^0, 4x^3 respectively
+ * 2. Variables e.g. y in 3y^2
+ * 3. Exponents e.g. 5 in y^5
+ *
+ * Class Polynomial constructs the polynomial using Array as an argument.
+ * The members of array are coefficients and their indexes as exponents.
+ */
+class Polynomial {
+  constructor (array) {
+    this.coefficientArray = array // array of coefficients
+    this.polynomial = '' // in terms of x e.g. (2x) + (1)
+    this.construct()
+  }
+
+  /**
+   * Function to construct the polynomial in terms of x using the coefficientArray
+   */
+  construct () {
+    this.polynomial = this.coefficientArray.map((coefficient, exponent) => {
+      if (coefficient === 0) {
+        return '0'
+      }
+      if (exponent === 0) {
+        return `(${coefficient})`
+      } else if (exponent === 1) {
+        return `(${coefficient}x)`
+      } else {
+        return `(${coefficient}x^${exponent})`
+      }
+    })
+      .filter((x) => {
+        if (x !== '0') {
+          return x
+        }
+      })
+      .reverse()
+      .join(' + ')
+  }
+
+  /**
+   * Function to display polynomial in terms of x
+   * @returns {String} of polynomial representation in terms of x
+   */
+  display () {
+    return this.polynomial
+  }
+
+  /**
+   * Function to calculate the value of the polynomial by substituting variable x
+   * @param {Number} value
+   */
+  evaluate (value) {
+    return this.coefficientArray.reduce((result, coefficient, exponent) => {
+      return result + coefficient * (Math.pow(value, exponent))
+    }, 0)
+  }
+}
+
+/**
+ * Function to perform tests
+ */
+const tests = () => {
+  const polynomialOne = new Polynomial([1, 2, 3, 4])
+  console.log('Test 1: [1,2,3,4]')
+  console.log('Display Polynomial ', polynomialOne.display())
+  // (4x^3) + (3x^2) + (2x) + (1)
+  console.log('Evaluate Polynomial value=2 ', polynomialOne.evaluate(2))
+  // 49
+
+  const polynomialTwo = new Polynomial([5, 0, 0, -4, 3])
+  console.log('Test 2: [5,0,0,-4,3]')
+  console.log('Display Polynomial ', polynomialTwo.display())
+  // (3x^4) + (-4x^3) + (5)
+  console.log('Evaluate Polynomial value=1 ', polynomialTwo.evaluate(1))
+  // 4
+}
+
+tests()