Add Basic Prefix Sum Algorithm

Author: Virus2hell

PrefixSum/BasicPrefixSum.js

@@ -0,0 +1,30 @@
+/**
+ * BasicPrefixSum.js
+ * Implementation of Prefix Sum array.
+ *
+ * @param {number[]} arr - Input array of numbers.
+ * @returns {number[]} Prefix sum array.
+ * @throws {TypeError} If input is not an array of numbers.
+ *
+ * Explanation:
+ * Given [1,2,3,4], returns [1,3,6,10]
+ */
+
+export function basicPrefixSum(arr) {
+  // Validate input
+  if (!Array.isArray(arr) || arr.some((x) => typeof x !== 'number')) {
+    throw new TypeError('Input must be an array of numbers')
+  }
+
+  // Handle empty array
+  if (arr.length === 0) return []
+
+  const prefix = new Array(arr.length)
+  prefix[0] = arr[0]
+
+  for (let i = 1; i < arr.length; i++) {
+    prefix[i] = prefix[i - 1] + arr[i]
+  }
+
+  return prefix
+}

PrefixSum/BasicPrefixSum.test.js

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+import { describe, it, expect } from 'vitest'
+import { basicPrefixSum } from './BasicPrefixSum.js'
+
+describe('Basic Prefix Sum', () => {
+  it('should compute prefix sum of a normal array', () => {
+    const arr = [1, 2, 3, 4]
+    const expected = [1, 3, 6, 10]
+    expect(basicPrefixSum(arr)).toEqual(expected)
+  })
+
+  it('should return empty array for empty input', () => {
+    expect(basicPrefixSum([])).toEqual([])
+  })
+
+  it('should throw TypeError for non-numeric array', () => {
+    expect(() => basicPrefixSum([1, 'a', 3])).toThrow(TypeError)
+  })
+
+  it('should handle single element array', () => {
+    expect(basicPrefixSum([5])).toEqual([5])
+  })
+
+  it('should handle negative numbers', () => {
+    expect(basicPrefixSum([-1, -2, -3])).toEqual([-1, -3, -6])
+  })
+})